leading to its surrender on February 6, 1862, before Grant's infantry even arrived. Grant then ordered an immediate assault on Fort Donelson, which dominated the Cumberland River. Fort Donelson, unlike Fort Henry, had a force equal to Grant's army. Unaware of the garrison's strength, Grant, McClernand, and Smith positioned their divisions around the fort. The next day McClernand and Smith independently launched probing attacks on apparent weak spots but were forced to retreat by the Confederates. On February 14, Foote's gunboats began bombarding the fort, only to be repulsed by its heavy guns. Seizing the initiative, the next day, Pillow fiercely attacked and routed one of Grant's divisions, McClernand's. Union reinforcements arrived, giving Grant a total force of over 40,000 men. Grant was with Foote, four miles away when the Confederates attacked. Hearing the battle noise, Grant rode back and rallied his troop commanders, riding over seven miles of freezing roads and trenches, exchanging reports. When Grant blocked the Nashville Road, the Confederates retreated back into Fort Donelson. On February 16, Foote resumed his bombardment, which signaled a general attack. Confederate generals John B. Floyd and Pillow fled, leaving the fort in command of Simon Bolivar Buckner, who submitted to Grant's demand for "unconditional and immediate surrender". Grant had won the first major victory for the Union, capturing Floyd's entire rebel army of more than 12,000. Halleck was angry that Grant had acted without his authorization and complained to McClellan, accusing Grant of "neglect and inefficiency". On March 3, Halleck sent a telegram to Washington complaining that he had no communication with Grant for a week. Three days later, Halleck followed up with a postscript claiming "word has just reached me that ... Grant has resumed his bad habits (of drinking)." Lincoln, regardless, promoted Grant to major general of volunteers and the Northern press treated Grant as a hero. Playing off his initials, they took to calling him "Unconditional Surrender Grant". Shiloh (1862) and aftermath With great armies now massing, it was widely thought in the North that another western battle might end the war. Grant, reinstated by Halleck at the urging of Lincoln and Secretary of War Edwin Stanton, left Fort Henry and traveled by boat up the Tennessee River to rejoin his army with orders to advance with the Army of the Tennessee into Tennessee. Grant's main army was located at Pittsburg Landing, while 40,000 Confederate troops converged