For the most part, combat stayed the same. In the American Civil War the combat was linear combat between regiments and brigades, each side trying to outflank the other or amass enough strength against a point in the enemy's line to break it. Toward the end of the war, as the South's manpower began to run dry (the South in the war enlisted some 800,000 white men out of a total white population of 5,000,000, quite the sizable population chunk), the South turned more and more to static defense, preparing elaborate trench networks in the face of Union assaults; perhaps the best example is Cold Harbor, where the Confederates in their trenches cut down some 13,000 Union troops at the cost of 5,000 of their own.

The war, however, was not decided by tactics; rather, it was decided by the fact that the Confederates did not have the industry nor the manpower to challenge Union hegemony forever. Though, the fact that the Union (in the later stages of the war) had cut the Confederacy in half by seizing the Mississippi and destroying Southern factories wherever they could certainly didn't help them much.