WASHINGTON  This is the season when defense secretaries typically sit for hours, hat in hand, before Congressional committees to plead for more money and then journey to the military academies to give perfunctory speeches about patriotism before young cadets.

But this year, Defense Secretary Robert M. Gates has not followed the script.

He sharply criticized members of the House of Representatives this week for spending money on Humvees that the Army did not want instead of buying surveillance systems needed to protect troops. In recent speeches, he has rebuked military leaders for clinging to ancient concepts of war  and by ancient he means before Sept. 11, 2001. And he has cited the painful experiences still unfolding in Afghanistan and Iraq to warn of grave risks if the military again intervenes in the Muslim world, this time in Libya, using tones far more grim than others in the Obama cabinet.

Even for a particularly outspoken defense secretary, Mr. Gates has reached a new level of candor. Perhaps he feels liberated by the fact that he is retiring soon and leaving Washington, a city, he has said, “where so many people are lost in thought because it’s such unfamiliar territory.”

Mr. Gates’s independence is a reminder that if he leaves this year  as he has insisted he will  his departure will kick off a search that will help define the administration. Will the president choose someone as outspoken, with a bipartisan pedigree that allows him to criticize the conduct of combat and makes him acceptable to Republicans?