Why did Lincoln instate martial law and suspend the writ of habeas corpus?

Lincoln instate martial law and suspend the writ of habeas corpus to stop the movement of Confederate troops on Washington.

Explanation:

In the year 1861 at the state of Maryland President Lincoln primarily suspended the Habeas corpus to bring a large number of civilian demonstrators into the military court and to stop the confederate troops marching towards Washington.

On the day of September 15, 1863, President Lincoln used his presidential powers to suspend the Habeas corpus all over the Union of those cases involving army man, conspirator, moles and war prisoners. This suspension order was in the long run extended based on the threat perception in the union.