Answer:
1. Gettysburg
2. Called to end slavery in the South (Confederacy)
3. Vicksburg
4. Suspending the right of habeas corpus (prisoner taken before judge before imprisonment), so he could quickly jail confederate sympathizers in the North to preserve the union
Explanation:
1. The Battle of Gettysburg took place on July 1 - 3, 1863 in and around the town of Gettysburg, Pennsylvania between Union and confederate forces during the American Civil War. It is considered as the turning point of the war, where the Army of the Potomac lead by Major General George Meade defeated attacks by the Army of Northern Virginia lead by Confederate General Robert E Lee, preventing Lee's invasion of the North.
2. The Emancipation Proclamation was issued by President Abraham Lincoln on January 1, 1863 and declared "all persons held as slaves are, and henceforward shall be free" within the confederate states. The Emancipation Proclamation only applied to states that had broken away from the United States, and exempted parts of the Confederacy that had come under control of the North.
3. The victory at the siege of Vicksburg, Mississippi in 1863 gave control of the Mississippi River to the Union during the American Civil War. By having control of the river, the Union forces would split the Confederacy in two and control a major route for transporting men and supplies.
4. Facing the crisis of the civil war in 1861, President Abraham Lincoln invoked his "war power" as commander in chief in order to take any measure to defeat the enemy. He suspended the privilege of the writ of habeas corpus by presidential decree, as well as declaring martial law, authorizing the trial of civilians by military courts and proclaiming emancipation of slaves, on account that in an emergency situation he may do things on military grounds which couldn't be done constitutionally by congress.