Answer would be the withdrawal of federal troops from the South.
one main reason why it started is because of different views on slavery and whether or not it should be legal also the election of abraham lincoln as president. hope this helped
On May 7, 1915, a german submarine torpedoed and sank the Lusitania, a British cruiseliner which had 128 American citizens on board, as well as military goods. It was the first step to the US joining the war.
hope this helps
