Why was there a civil war in the United States?

Cambridge IGCSE History 0470 · Paper 1 Section A, Core Content Option A Syllabus: 2027 and 2028 Option A: The nineteenth century: the development of modern nation states, 1848 to 1914 Key Question 4 of six

This file covers the American Civil War as Core Content, which means the causes of the war, the reasons for the Union victory, and Reconstruction down to 1877. If you are looking for the Wall Street Crash, the New Deal, Prohibition or the 1920s Ku Klux Klan, you are in the wrong file: that is Depth Study D, a different period and a different set of questions. Nothing below goes past 1877.

The Key Question has two halves joined by an "and", and that is not decoration. Cambridge sets questions on the causes and questions on the results in roughly equal numbers, and a student who has revised only the road to Fort Sumter will meet a 10 mark question on the Freedmen's Bureau about as often as not.

1. What the syllabus actually asks

This is the wording printed in the Cambridge IGCSE History 0470 syllabus for 2027 and 2028. Learn the Key Question itself, because examiners build 10 mark questions straight out of it.

Key Question 4

Why was there a civil war in the United States and what were its results?

Focus points

• How far did slavery cause the Civil War?
• What was the significance of Lincoln's election as president?
• Why was the North able to win the war?
• Did the war change anything?

Specified content

• Causes and consequences of the American Civil War, 1820 to 1877:
• differences between North and South
• slavery, slave states and free states, abolitionism
• the 1860 election and secession of the Southern states
• reasons for the North's victory and the South's defeat
• the role of Lincoln
• reconstruction and the extent of its success

The focus points are four essay titles

Cambridge defines the layers itself: key questions define the over-arching issues, focus points identify the issues that enable candidates to gain an understanding of the key question, and specified content provides guidance on what needs to be studied.

So do not read the four focus points as four chapters. Read them as four arguments you must be able to run in both directions.

Every one of those four has been set as a real 10 mark question, several of them many times over.

One thing to notice about the dates

The option header says the nineteenth century 1848 to 1914, but the specified content for this Key Question says 1820 to 1877. The specified content governs. Cambridge really does set part (a) questions on the Missouri Compromise of 1820, twenty-eight years before the option's own start date, and 10 mark questions that run to 1877. Revise the full span.

2. Where this Key Question sits on the paper

The level ladders, the assessment objective split and the two rules Cambridge changed for the 2024 series are the same for every question on Paper 1, and they are set out in the How Cambridge marks History 0470 Paper 1 notes. Read that page once. Nothing below repeats it.

What is specific to this Key Question is where it lands and what it tends to ask.

It is usually Question 3. Of the 48 Paper 1 mark schemes read for these notes, covering 2018 to 2024, 38 set a question on this Key Question. It was Question 3 in 30 of them, Question 2 in five and Question 4 in three. In the ten papers that skipped it, the two questions from Key Questions 4 to 6 went to empire and the First World War instead. So the odds are good but not certain, and the question number is a strong habit rather than a rule.

The two halves are set almost evenly. Across those 38 papers, the 10 mark part broke down like this:

Causes and results are therefore about level, with the war itself a clear third. Half-revising this topic is a real gamble.

But the 6 mark question is a different story. Of the 38 papers, only one set part (b) on why the North won. The 6 mark question is almost always either a pre-war cause (the Fugitive Slave Act, the Dred Scott case, Kansas, the Missouri Compromise, why the South supported slavery) or Reconstruction (Johnson and Congress, the Freedmen's Bureau, carpetbaggers, the Ku Klux Klan). The military side of the war is a 10 mark topic and almost nothing else. Weight your revision accordingly: know the war's outcome as an argument, and know the compromises and Reconstruction as detail.

It has twice been the Paper 2 topic. Paper 2 sets one prescribed source topic for Option A each series. In the corpus read here, the nineteenth century topic came from this Key Question in two full series: November 2020, on John Brown and the violence in Kansas, and June 2022, on the Ku Klux Klan and on how far Lincoln caused the split of 1860 to 1861. When that happens the same revision pays on two papers, though Paper 2 asks what the sources show, never what caused what.

A warning about examiner reports on this topic

Option A is the minority choice. Series after series, the Principal Examiner report prints, under the nineteenth century heading, that there were too few responses for any meaningful comments to be made. Only a handful of reports across 2018 to 2024 say anything at all about this Key Question. Section 8 gathers everything that was said. It is short because Cambridge's own commentary is short, not because the traps are few.

3. Focus point: how far did slavery cause the Civil War?

This is the most-set 10 mark question in the whole Key Question, and Cambridge asks it in at least six wordings: was the war fought to end slavery, was it fought over slavery, was it fought over states' rights, was Lincoln's election the main cause, was secession the main cause, was the Kansas-Nebraska Act the most important cause.

They all reduce to the same argument, so learn it once.

The two sides Cambridge actually credits

Slavery was the cause. Cambridge's own Level 3 wording: slavery was crucial to the economy of the South, because without slaves it would have been difficult to keep the profitable cotton industry going, and it was also a way of keeping black Americans under control and ensuring white supremacy. Most Southerners believed an end to slavery would bring economic collapse, race wars and the disintegration of their society. So Northern criticism of slavery was heard as a threat to everything.

States' rights was the cause. Cambridge's own Level 3 wording on the other side: the South believed the rights of the Federal Government were threatening the rights of individual states, and it was particularly worried because the population of the North was growing faster than the South's. Soon the North would control the Federal Government. That is why the South did not want Washington interfering inside individual states.

The judgement that reaches Level 5

Cambridge prints its own model judgement, and it is worth learning as a sentence shape because it dissolves the false choice rather than picking a side blindly. In the June 2024 scheme, the top-band answer says states' rights were not the main cause, because that issue only became important because of slavery: when threats to slavery appeared, the South used states' rights as its defence against interference from Washington, and the issue it cared about most was slavery.

1. slavery is the interest
2. states' rights is the constitutional weapon chosen to defend it
3. so the two are not rivals, one is the tool of the other

Use that shape. It answers "how far" precisely, and it explains why the other side exists at all.

The chain of compromises, and why each one broke

The specified content asks for slave states and free states, and this is where that lives. Each of these has been a part (a) or part (b) question in its own right, so learn the terms, not just the names.

The Missouri Compromise, 1820. Missouri applied to join the Union as a slave state. At the time there was an equal balance of free and slave states, so admitting Missouri would give the slave states a majority. Maine was admitted as a free state in 1820 to hold the balance, Missouri came in as a slave state, and a northerly limit was fixed above which slavery was not allowed in the Louisiana Purchase lands. Henry Clay proposed the version that passed and President James Monroe signed it. It lasted until 1854.

The annexation of Texas, 1845. Controversial because nobody knew whether Texas would be slave or free, and because it was large enough to be split into five separate states. If all five were slave states the free states would be outnumbered. Mexico still claimed the territory, and the war that followed, which Cambridge dates 1846 to 1848, ceded Utah and New Mexico.

The Compromise of 1850. California admitted as a free state. The slave trade abolished in the District of Columbia, though slavery itself could continue there. Utah and New Mexico organised under popular sovereignty, meaning the settlers decided. Texas gave up much of its western land claim and received $10,000,000 to pay off its debt. And a harsher Fugitive Slave Act.

The Fugitive Slave Act of 1850 is the single most useful item in this section, because it is the one that made Northerners personally complicit. Captured runaways had to be returned. Officials and citizens of free states had to obey. Officials who failed to arrest a runaway were fined; officials who captured one were promoted. Suspects got no jury trial and could not testify for themselves. Anyone helping a runaway was fined and imprisoned. The commissioner was paid $10 if a fugitive was returned to slavery and $5 if the fugitive was set free.

1. a Northerner who had never held an opinion on slavery is now required by law to enforce it
2. the choice is break the law or act against your own belief
3. indifference in the North turns into opposition

That chain is Cambridge's own reasoning, almost word for word, and it is why the Act shows up as a part (b) three separate times.

Uncle Tom's Cabin, by Harriet Beecher Stowe. Cambridge credits it as a cause in its own right and prints one figure: it sold over 300,000 copies in its first year.

The Kansas-Nebraska Act, 1854. Split the Nebraska territory into Kansas and Nebraska, let the settlers of a territory decide whether slavery would be allowed, and in doing so dissolved the Missouri Compromise. Cambridge notes it also dealt with western expansion and a transcontinental railroad.

Bleeding Kansas. Pro-slavery "border ruffians" came in from Missouri to swing elections; Northern settlers came in to support the Free-Soilers. Two rival governments were set up by 1855. President Pierce sent US troops to Topeka in 1856 and pitched battles were fought that year. The new territorial governor, John W Geary, restored some order after 1856. Kansas entered the Union as a free state in 1861.

The Dred Scott case, 1857. The Supreme Court ruled against Scott: slaves could not be American citizens, black Americans could not claim citizens' rights, states could not change that by granting state citizenship, the Court therefore had no jurisdiction, slave owners could not be deprived of property protected by the Fifth Amendment, the Missouri Compromise was unconstitutional, and slavery could not be banned in the territories.

Harpers Ferry, 1859. John Brown and a small force attacked the arsenal expecting slaves to join them. He was captured and hanged. Be careful with the details here: see section 9.

The Free Soilers, whom Cambridge sets as a part (a) in its own right, were an anti-slavery party active from 1848 to 1854 who opposed the expansion of slavery into the western territories, supported land reform, and many of whom later joined the Republican Party.

4. Focus point: what was the significance of Lincoln's election as president?

This is the hinge between the two halves of the Key Question, and it is asked at all three mark tariffs.

Why the South was alarmed

Cambridge's own Level 3 answer: Lincoln was hated in the South, where many saw him as a radical abolitionist and therefore a threat both to slavery and to a way of life. They feared he would repeal the Fugitive Slave Act and surround the South with more and more free states, which would make slavery increasingly difficult to maintain. Other credited fears: that his election would encourage slave uprisings, and that it threatened the independence of the Southern states. The June 2018 examiner report adds two points candidates raised well: Lincoln was not on the ballot in the South, and he had promised to raise tariffs.

1. Lincoln wins without a single Southern vote
2. the South concludes it can be governed by a section that will never need its consent
3. secession is reframed from rebellion into self-defence

Secession, and the Confederacy

South Carolina seceded first, in December 1860. Mississippi, Florida, Alabama, Georgia, Louisiana and Texas followed in January and February 1861. In February 1861 representatives of the seceded states met at Montgomery, Alabama, and formed the Confederate States of America. On 9 February they elected Jefferson Davis of Mississippi as their first president.

Why secession became war

Cambridge sets this as a part (b), and the credited answer is a failure to compromise on both sides. Congressional attempts at a settlement, such as the Crittenden proposals, were rejected by the Republicans and defeated in Congress, and Confederate leaders would have rejected them anyway. President Buchanan did nothing and allowed federal forts and arsenals in the South to be taken over. Lincoln held that secession was illegal and that the Union was unbreakable.

Fort Sumter, April 1861. The US Army held the fort, Confederate forces besieged it, the garrison ran short of supplies, Lincoln sent supply ships, the Confederates demanded evacuation and then bombarded the fort, and the US troops agreed to evacuate. Cambridge calls it the first battle of the Civil War. Lincoln then ordered a blockade of the Confederacy and issued a call to arms to put down what he called a rebellion.

5. Focus point: why was the North able to win the war?

Nine of the 38 papers set the 10 mark question here, and every single one of them is the same argument dressed differently: resources against leadership. Cambridge has asked whether the North won because of skilful military leadership, because of economic advantages, because of Lincoln, whether the South lost because its economy was weak, whether economic factors mattered more than leadership, and how surprising the defeat of the South was.

The resources side

These are Cambridge's own figures, printed in its mark schemes. Use them; they are exactly the kind of specific contextual knowledge that lifts a Level 3 explanation.

• The North had 85 per cent of the industry, so it could mass-produce weapons and supplies.
• The North had 80 per cent of the free population.
• The North had 70 per cent of the railways.
• The Confederacy had 11 states against the North's 25, in Cambridge's count.
• The North had a sizeable navy and used it to blockade the South, which stopped weapons coming in and stopped raw cotton going out. The South's population was then too small to raise enough tax to fund its army.
• The South printed too much money, which caused inflation, wrecked its economy and destroyed morale.

The leadership side

• Lincoln set a clear and consistent war aim, to preserve the United States, and held the North to it.
• He worked to keep the border states loyal, which is why he overruled General Fremont's order in Missouri to free slaves. Cambridge notes that four Southern states stayed loyal to the Union, which created problems for the Confederacy.
• The Emancipation Proclamation opened the Union army to black Americans, made the war a moral cause, and made it much harder for Britain and France to back the South without appearing to back slavery.
• Grant won at Fort Donelson and Vicksburg, became overall commander in 1864, ran the Overland Campaign in Virginia and finally defeated Lee.
• Sherman captured Atlanta and then made the March to the Sea in 1864, from Atlanta to Savannah, using a scorched earth policy that destroyed military, industrial and civilian targets, disrupted the Confederate economy and, in Cambridge's words, destroyed the South's will to fight.
• Against that, Cambridge credits Southern mistakes: Lee's offensive strategy cost casualties the South could not replace, he focused on Virginia and lost the West, and the South fought a conventional war when guerrilla warfare might have exhausted Northern patience.

The judgement

Cambridge's own top-band sentences are careful, and they are not "both sides had a point":

• On the economic question: being economically stronger let the North wage a long war and was crucial, however good leadership was needed to make use of those advantages and that was the decisive factor.
• On Lincoln: Lincoln was not responsible for the defeat of the South, because the North's economic advantages made Union victory likely in the long run.
• On surprise: the defeat was neither a surprise nor not a surprise, because at the start both sides had strengths and either could have won, and the length of the war and the scale of the casualties prove it.

1. the North's resources make victory possible
2. leadership decides whether that possibility is converted
3. so resources set the ceiling and leadership set the timing

6. Focus point: did the war change anything?

Fourteen of the 38 papers put the 10 mark question here, which makes this half of the Key Question as heavily examined as the causes. It is also the half students under-revise.

What changed on paper

The three amendments. Cambridge's own dating: the 13th Amendment ended slavery and was added to the Constitution in December 1865. The 14th Amendment was passed in April 1866 and gave all citizens equality before the law. The 15th Amendment was introduced in 1869 and ratified in 1870, making it illegal to deny the vote on grounds of colour or race. See section 9 for a wrinkle in how Cambridge names the 14th.

The Freedmen's Bureau. Its work is the most-credited single success of Reconstruction. It helped freed people find family members separated during the war, provided health care, clothing, education and jobs, monitored local courts so that black Americans got justice, and tried to ensure fair contracts of employment. It confiscated planter property to set up schools, and Cambridge's own exemplar says 90,000 former slaves were being educated by 1865, with hundreds of hospitals providing free medical help to half a million patients. Its work was stopped in 1872.

President Grant. Cambridge credits him with signing the Fifteenth Amendment, the Force Acts against the Ku Klux Klan, laws in 1871 strengthening federal power against terrorism aimed at black Americans, and the 1875 Civil Rights law banning racial discrimination in public transport and stopping black Americans being excluded from jury service.

What did not change

The Black Codes. Introduced by many Southern states after the war to keep white power: they limited the jobs black Americans could hold, allowed arrest, beating and forced labour for breaking a labour contract, were designed to stop black Americans voting, and led to racial segregation.

The Ku Klux Klan. Founded by ex-Confederate soldiers who saw themselves as vigilantes, it grew rapidly from the 1860s. Cambridge's Level 3 wording: it aimed to restore white supremacy, drive black Americans out of politics by intimidation and murder, destroy the Republican administrations set up in the South, and restore white control of black labour. It was hard to prosecute because witnesses were afraid to testify and juries let members off. Similar white militias such as the White League did the same work.

No land. The single most-repeated point in Cambridge's Reconstruction schemes is that there was no redistribution of land. Most black Americans owned little and stayed poor. Sharecropping and tenant farming left black farmers in permanent debt and at the mercy of their former masters.

Andrew Johnson. Cambridge treats him as the personified failure of Reconstruction, and sets him as the named culprit in two separate 10 mark questions. He thought Reconstruction unnecessary, wanted the Southern states back easily, tried to reduce the power of the Freedmen's Bureau and vetoed its extension, did not support the Military Reconstruction Act, issued thousands of pardons to ex-Confederates, and ordered land returned to former Confederate owners, which meant freedmen were evicted.

Congress pushed back. When Johnson vetoed the Bureau extension the Republicans joined forces to pass a Civil Rights Act. The Basic Reconstruction Act put in military governors and governments elected by universal suffrage, but disqualified Confederate leaders from voting and barred former Confederate politicians from standing.

Carpetbaggers and scalawags. Carpetbaggers were Northerners who came South seeking election, backed by Union troops, who took control of state governments in the Deep South and were often corrupt. Cambridge also credits the other reading of them: that they supported Republican policies and the right of black Americans to vote, invested in the South and wanted to reform it to be more like the North. Scalawags were white Southerners who supported Reconstruction and the Republicans.

1877. White Southerners and Democrats regained control, President Hayes ended Reconstruction, Jim Crow laws brought segregation, and many black Americans were disenfranchised by new laws. Cambridge's own balancing point: the South's economy began to recover from 1867, the Union had been preserved, secession was repealed, and most white Southerners committed themselves to the Union.

The judgement

Cambridge's printed Level 5 answer on Johnson is the model, and it moves the blame off the individual: Presidents like Johnson and Grant have been blamed, but both faced a wrecked Southern economy and needed the cooperation of white Southerners whose attitudes had not changed, and against those attitudes there was little any President could do.

1. the war and the amendments changed the law
2. the law was enforced by Southern courts, juries and sheriffs
3. so legal freedom arrived without the power to use it

Balance the two halves honestly. Cambridge credits both "black people did have more control over their lives than under slavery" and "black sharecroppers lived in permanent debt" in the same mark scheme.

7. Judgement sentences for this topic

The tenth mark is a separate act, as the How Cambridge marks History 0470 Paper 1 notes explain. Here are shapes that fit this content and state a position with a reason attached:

• "States' rights was the language, but slavery was the interest, because the argument about states' rights only became urgent once slavery was threatened."
• "Lincoln's election did not create the divide, it proved that the divide could no longer be voted away."
• "The North's resources made victory likely, but leadership decided how long it took and how much it cost."
• "Reconstruction changed the law and left the power where it was, which is why freedom on paper produced sharecropping in practice."
• "The war achieved more than Reconstruction for black Americans, because emancipation could not be repealed and almost everything Reconstruction built could."

8. The mistakes examiner reports name on this content

The general faults belong to the How Cambridge marks History 0470 Paper 1 notes. These are the ones Cambridge names on this topic specifically. There are few of them because most reports say there were too few Option A responses to comment on at all.

• Repeating the question back in part (a). On John Brown, the report notes candidates who wrote only that he was an abolitionist, which the question stem had already said. Nothing that is already printed in the question can earn a mark.
• Skipping part (a) altogether. The June 2019 report records that a number of candidates who chose Question 3 simply left part (a) blank. That is four marks abandoned in a paper worth sixty.
• Describing slavery instead of explaining it. Asked why slavery existed in the Southern states, candidates described the conditions in which slaves lived. Conditions are not a reason. The reason is cotton, profit and the labour the plantations needed.
• Asserting that nothing improved. On Reconstruction, the report notes many candidates stating flatly that life for former slaves did not get any better, without substantiating it. The examiner asks for specific reference to the effects of Reconstruction. "Nothing changed" is a Level 1 sentence until the Black Codes, the absent land redistribution or the Klan is attached to it.
• One-sided answers on the causes. In the series where the question was whether the war was fought to end slavery, the report records that the explanations agreeing with the statement were stronger than those disagreeing. The states' rights side is the one candidates under-prepare, and on a "how far" question that is the side that is worth marks.

9. Where Cambridge's own materials disagree

Three places. Do not try to reconcile them, and do not build an answer on the disputed detail.

The Missouri Compromise line. One mark scheme says a line of latitude was fixed above which slavery was not allowed and then calls it the Mason-Dixon Line. A different mark scheme says no slavery was allowed above the 36 degrees 30 minutes latitude line. Those are not the same line. Write "a line of latitude was fixed above which slavery was banned in the Louisiana Purchase lands", which both schemes support, and leave the name out.

The date of the Emancipation Proclamation. Cambridge sets a 6 mark question that says "Why did Lincoln issue the Emancipation Proclamation in 1862?" and prints an exemplar elsewhere that says "the Emancipation Proclamation of 1863". If a question gives you a date, use that date. If it does not, write "the Emancipation Proclamation" without one.

Harpers Ferry. The November 2020 Paper 2 sources disagree on how many men John Brown had, 18 or 21, and on where he was hanged, Richmond or Charleston. The examiner report treats spotting that disagreement as the skill being tested. So do not quote a number for Brown's force on Paper 1 either.

One more to handle carefully rather than as a conflict: Cambridge's mark schemes repeatedly write that the 14th Amendment was the Civil Rights Act, dating it to April 1866. Other schemes describe a separate Civil Rights Act passed by Congress after Johnson's veto. Say what the amendment did, which is that it gave all citizens equality before the law, rather than what it was called.

10. Quick revision

• Question 3, most of the time. 38 of 48 mark schemes from 2018 to 2024 set this Key Question; 30 of those were Question 3.
• Causes 15, victory 9, results 14 at the 10 mark tariff. The two halves of the Key Question are set almost evenly, so revise both.
• The 6 mark question is almost never about the war itself. One paper in 38. It is the compromises or it is Reconstruction.
• The causes argument is always the same: slavery against states' rights. Cambridge's own top answer is that states' rights was the weapon and slavery was the interest.
• The victory argument is always the same: resources against leadership. 85 per cent of industry, 80 per cent of the free population, 70 per cent of the railways, 11 states against 25, and the blockade, set against Lincoln, Grant and Sherman.
• The Fugitive Slave Act of 1850 is the highest-yield single item on the causes side, because it explains how Northern indifference became Northern opposition.
• On results, lead with what did not change: no land redistribution, the Black Codes, the Klan, sharecropping. Balance it with the three amendments and the Freedmen's Bureau.
• Nothing after 1877. The 1920s Klan and the New Deal belong to the Depth Study, not here.

11. Syllabus map

12. Where these facts come from

Everything above is taken from Cambridge's own documents, and every claim can be checked against a named one.

The Cambridge IGCSE History 0470 syllabus for 2027 and 2028. The Key Question, the four focus points and the specified content, all quoted as printed; the option title and its 1848 to 1914 dating; the definitions of key question, focus point and specified content.

Paper 1 mark schemes, 2018 to 2024, all 48 read. The count of 38 papers setting this Key Question and the question-number distribution; the split of 10 mark questions into causes, victory and results; the observation that only one paper set part (b) on why the North won. Every figure, term and date in sections 3 to 6 comes from the indicative content or the printed exemplar answers of a named scheme, including the 85, 80 and 70 per cent figures, the 11 against 25 states, the $10 and $5 commissioner fees, the $10,000,000 paid to Texas, the 300,000 first-year sales of Uncle Tom's Cabin, the 90,000 pupils and half a million patients of the Freedmen's Bureau, and the amendment dates. The Level 5 judgements quoted in sections 3, 5 and 6 are Cambridge's own printed top-band answers.

Paper 2 question papers, 2018 to 2024. The two series in which the Option A prescribed topic came from this Key Question.

Principal Examiner reports, 2018 to 2024. Section 8 in full, and the repeated statement that there were too few Option A responses for meaningful comment, which is why section 8 is short.

Not verified, and deliberately absent. Casualty totals, the size of either army, battle dates other than those Cambridge prints, the popular vote in 1860, the number of enslaved people in 1860, and the date the Civil War ended. This topic has a very large popular literature and it is easy to write a confident number from memory. None of those figures appears in the 0470 corpus read for these notes, so none of them appears above. If a question needs one, Cambridge will have given it to you in the stem.

Not the topic you were looking for? Describe what you are stuck on in your own words and we will take you to the notes that answer it.