 Complete the following phrase:  On April 15, 1861, Abraham Lincoln called up 75,000 militiamen to put down an insurrection of southern states after Confederate forces attacked Fort Sumter on April 1214, 1861. Mathew B. Brady, one of the preeminent photographers of the day, secured permission from President Lincoln to follow the troops, for what everyone thought would be a short and glorious war. He only saw the first major engagement, 