After the secession of Mississippi, Davis left the senate on Jan 21, 1861 and returned to Miss as commander of his own State's troops. Davis hoped for a military career in case of war. Instead, to his surprise and regret, he was unanimously chosen by the Confederate Provisional Congress as Provisional President of the Confederate States on Feb. 9, 1861.
He was inaugurated in Montgomery on Feb 18, and was formally elected by the people on Oct. 16, and again inaugurated, this time at Richmond, Va. under the "permanent constitution" on Feb 22, 1862. As we all know he was still President of the CSA when the Confederacy collapsed.
Davis and his cabinet sought to negotiate for a withdrawal of the Union troops from military posts in the South, and he did not order military operations to be opened at Charleston in April of 1861 until he was convinced that the Lincoln administration had sent an armed expedition to reinforce the garrison of Fort Sumter.
The easy victory at Bull Run on July 21 misled the South and even Davis into believing that its independence would be won without great effort. Thus he did not capitalize on the war ardour of the first months of the struggle.
Through much hard work coupled with good commanders, 1862 brought a number of brilliant victories in Virginia, but it was otherwise on the Mississippi. Unfortunately his greatest blunder was to decide on an offensive in the East instead of reinforcement of the army on the Mississippi. When Gettysburg failed, and the next day Vicksburg fell, the Confederacy was cut in half.