To what extent was slavery the key cause of the US Civil war?

westward expansion to spread slavery. Polk’s ideas angered and worried the north and caused relations to break down further due to a lack of trust. At The very beginning of the Mexican war the north issued the Wilmot Doctrine that proposed that any territory gained from Mexico should exclude slavery. This was very unpopular in the south as they wanted and needed to expand slavery if it had any chance of surviving and so caused great tension inside and outside of Congress. To battle this the south proposed a series of resolutions under the name, The Calhoun Doctrine, which stated that any slave owner had the right to take his property into any free or slave state if he or she decided to and that the Federal Government had no power in stopping them. This however effectively undermined the Missouri Compromise because it stated that slavery and slave could go anywhere.Popular sovereignty was a very successful compromise so that there could be a half way between these two rather extreme notions. Popular sovereignty stated that each state and territory could decide for itself if it wanted to become a slave state or a free state. This seemed fair and both the north and south backed it because it gave the south a chance to expand slavery and it gave the north a chance to stop slavery spreading any further. Although it did raise questions and inflamed the tension because both the north and south would pressure states to turning to their ideals, it also scared politicians because by using popular sovereignty a huge proportion of the country could become slave or free. The Fugitive slave act is also arguably one of the main causes to fire up tension over the question of slavery and in turn the path to civil war. It aggravated the north greatly, many sympathised with slaves and the north gave any fugitives a place to stay where they would be protected and most importantly free. However the south did not like this and threatened to secede from the union if it didn’t stop, It stated that any fugitive slaves could be recaptured even if in a free state and taken back to the south where they would be put back into slavery. The act was very unpopular in the north and caused a greater split between the north and south however it was seen as the price to pay to save the union and stop the south seceding. The collapse of the second party system also became a key cause of the civil war; the Whigs had already lost a huge amount of their support by appeasing the Catholics in the 1852 elections, but it was the Democrats that caused the second party system to crash. The Democrats were blamed for sponsoring the Kansas-Nebraska act and lost all but 23 of their previous free state seats in Congress and in the south they lost all but 4 from their previous 67. It was the Republican Party who stepped in to fill the void left by the Whigs and Democrats and in turn the Democrats caused huge amounts of tension in the south. This tension emerged after the Republicans released their party policies, which clearly showed they were completely against slave power and the expansion of slavery, however they did not believe in immediate abolition of slavery but still it gave the south a reason to worry and fear the Republicans getting into power.One event in Congress could have been the turning point of the Republicans gaining power however it also showed slave power for what it actually was. The event involved the attack on Senator Sumner by Congressman Brooks, where Brooks repeatedly beat Sumner with his cane so that his injuries were so bad that he did not return to Congress for 2 years. It showed that the south used slave power to silence free speech by using brute force. Another example of slave power, which caused great tension between the north and south was the incident in Kansas. Pro slavers tried to arrest free state leaders where dozens of free state people well killed, the north were outraged, the incident was only inflamed when pro slavers hurried to Kansas for the elections. Thousands of southerners voted for the Lecompton Government, a fixed party that was in full support of slavery. However to northern disbelief Buchanan accepted it as a legal government. This appeared to the north that Buchanan was under the influence of slave power, many northerners wanted slavery abolished completely.After the Dred Scott case it was clear to the north that there was a slave power conspiracy going on, the Supreme Court had undermined the Missouri Compromise by saying that slavery could be taken into any territory or state in America and that the Federal Government had no power to stop owners taking their property into free states. This greatly annoyed the North as they believed that slavery was completely immoral both economically and socially and did not want it in their free states, the south however saw this as an act of aggression and believe that they could take their slaves wherever they wanted to. It merely showed the north the social horrors of slavery and what had to be done to set things right. In the 1860 presidential elections, Lincoln the Republican Party leader and a known anti-slavery spokesmen won with 39% of the public vote. With Lincoln in power the south believed that the only way they could stop slavery from being abolished was to secede. On the 10th December 1860 South Carolina seceded from the Union and over the next year 10 more states seceded and so the north became the Union and the south became the Confederacy. The Confederacy set up its own government and appointed Jefferson Davis as their president; it set up an army, a navy and created its own flag. Although the north and south were completely separated and the tension had never been greater before there was still no war. The Confederacy had been taking over the unmanned arsenals in the south that belonged to the Union, however they could not take Fort Sumter and Fort Pickens. Fort Pickens was off the coast of Florida, out of range of shore batteries and could be easily reinforced by the Union navy, it was however Fort Sumter that would cause the tension. In January 1861 Buchanan sent a ship full of supplies to Major Robert Anderson who was in charge of the Fort. The Confederacy opened fire on the ship and it had to retreat but Anderson did not return fire. The Confederacy asked Anderson if he wished to surrender but he declined and so at 4.30 am on the 12th April the first shots of the civil war were fired. Slavery was undoubtedly the key cause of the civil war; it divided the north and the south in the first place and caused the south to attack the north at Fort Sumter in an effort to save slavery. Both sides were effectively fighting to keep slavery or abolish it and so it was the main cause of the American Civil war.