toward defining the war as a matter of ending slavery. Confederate invasion of Kentucky (September 1861) By mid-1861, eleven states had seceded, but four more slave-owning "border states" remained in the Union—Missouri, Kentucky, Maryland, and Delaware. Kentucky was considered the most at risk; the state legislature had declared neutrality in the dispute, which was seen as a moderately pro-Confederate stance. The loss of Kentucky might have been catastrophic because of its control of the strategic Tennessee and Ohio rivers and its position from which the vital state of Ohio could be invaded. Lincoln wrote, "I think to lose Kentucky is nearly the same as to lose the whole game." On September 3, 1861, Confederate General Leonidas Polk extended his defensive line north from Tennessee when Gideon Pillow occupied Columbus, Kentucky (in response to Ulysses S. Grant's occupation of Belmont, Missouri, directly across the Mississippi River). Polk followed this by moving through the Cumberland Gap and occupying parts of southeastern Kentucky. This violation of state neutrality enraged many of its citizens; the state legislature, overriding the veto of the governor, requested assistance from the federal government. Kentucky was never again a safe area of operation for Confederate forces. Ironically, Polk's actions were not directed by the Confederate government. Thus, almost by accident, the Confederacy was placed at an enormous strategic disadvantage. Indeed, the early Union successes in the Western Theater (the locale of all their successful large-scale non-naval initiatives until 1864) can be directly tied to Polk's blunder. Union capture of Forts Henry and Donelson (February 1862) The capture of Forts Henry and Donelson, and the Confederate surrender at the latter, were the first significant Union victories during the war and the start of a mostly successful campaign in the Western Theater. Ulysses S. Grant completed both actions by February 16, 1862, and by doing so, opened the Tennessee and Cumberland Rivers as Union supply lines and avenues of invasion to Tennessee, Mississippi, and eventually Georgia. The loss of control of these rivers was a significant strategic defeat for the Confederacy. This was the start of offensive actions by Grant that, with the sole exception of the Battle of Shiloh, would continue for the rest of the war. Albert Sidney Johnston's death (April 1862) Albert Sidney Johnston was considered one of the best generals serving in the Western Theater. By 1862, he commanded all Confederate forces between the Cumberland Gap and