Lincoln's assassins hoped that killing the president and other important governmental figures on April 14, 1865, would throw the U.S. government into confusion, allowing the Confederacy to remain independent. The assassins also tried to kill Vice President Andrew Johnson and Secretary of State William Seward.
Initially, Booth and his co-conspirators had planned to kidnap Lincoln in March 1865, but the plan fell through when the president did not show up where the conspirators thought he was supposed to be. The war was going badly for the Confederacy by that point, with Richmond falling and the Confederate army under Robert E. Lee surrendering to Union forces in early April.
Faced with imminent defeat, Booth and the other conspirators came up with one last, desperate plan to save the Confederacy. They orchestrated an elaborate plot to decapitate the American government. Booth would kill the president at Ford's Theater, while Lewis Powell would murder William Seward and George Atzerodt would assassinate Andrew Johnson. Booth was successful, but Powell merely wounded Seward, and Atzerodt did not even attempt to kill the vice president.
Unfortunately for the assassins, their actions did not lead to a resurgence of the Confederacy. In fact, they made conditions worse. Lincoln had been the primary advocate for a gentle peace, and his death radicalized the opponents of the rebellious states who imposed harsh conditions of surrender on the former states of the Confederacy.