Columbus blocked Union access to the lower Mississippi. Grant and General James B. McPherson planned to bypass Columbus and with a force of 25,000 troops, move against Fort Henry on the Tennessee River. They would then march ten miles east to Fort Donelson on the Cumberland River, with the aid of gunboats, opening both rivers and allowing the Union access further south. Grant presented his plan to Henry Halleck, his new commander in the newly created Department of Missouri. Halleck was considering the same strategy, but rebuffed Grant, believing he needed twice the number of troops. However, after Halleck telegraphed and consulted McClellan about the plan, he finally agreed on the condition that the attack would be conducted in close cooperation with the navy Flag Officer, Andrew H. Foote. Foote's gunboats bombarded Fort Henry, leading to its surrender on February 6, 1862, before Grant's infantry even arrived.