The Army of Kentucky was the second most-important Confederate States Army formation, after the Army of Northern Virginia. During the War of Secession and the Great War it defended the region against the U.S. Army, conquering Kentucky near the end of the first conflict. In the Second Mexican War it was responsible for repulsing the U.S. Army's attempt to conquer Kentucky, which was the principal battleground of that war. In the Second Great War, the Army of Kentucky was the Confederacy's principal offensive force in 1941, carving a corridor of occupation through Ohio between the Ohio River and Lake Erie in Operation Blackbeard. The Army of Kentucky was earmarked to continue the attack in following year for Operation Coalscuttle, driving east from Ohio into Pittsburgh, Pennsylvania before being trapped in a pocket by Irving Morrell and annihilated in early 1943.