Walker was the first of five persons (the others being, Benjamin, Randolph, Seddon and Breckinridge) who held the office of Confederate Secretary of War – serving in this cabinet position from Feb. 21 to Sept. 16, 1861.
Walker, a lawyer by profession and an ardent secessionist, had no military training.
From readings about him, although an energetic individual, Walker showed significant performance deficiencies in this role as a Cabinet Secretary. It seems he lacked diplomacy in his dealings with State governors and politicians, and often got into disputes with them. He also displayed a lack of awareness of the big picture, by making unrealistic predictions, like those about the shortness of the war and the premature capitulation of Washington D.C.. While he was apparently attributed with mobilizing large numbers of troops for service during his brief tenure, he is blamed for failing to adequately supply them with weapons and equipment in this same period.
Performance shortfall considerations aside, perhaps his unsuitability for any administrative leadership roles can be evidenced by his brief periods of service, as well as the manner of his departures, in these positions. In his cabinet job, it was apparently the stresses of the role that broke down his health, as well as disagreement with Davis over troop deployments in Kentucky, that largely led to him resigning from this role. His subsequent appointment by Davis the next day as a B-G, was followed with assignments in charge of garrisons at Mobile then Montgomery that did not last long either, before he abruptly resigned on March 31, 1862.
He probably found his true calling, when he was appointed as a military court judge (with the rank of Colonel) on April 6, 1864, until the end of the war.
Thought his most notable act while serving as Confederate Secretary of War, was issuing the order to Beauregard on April 11 to bombard Fort Sumter.