WASHINGTON — He's hardly a household word, but Jesse Brown, the 48-year-old former Marine who Thursday was nominated as secretary of veterans' affairs, has legions of friends in veterans' groups and on Capitol Hill.

"He's a quiet doer," said one congressional aide. "He is soft-spoken but firm."

Brown, the second African-American chosen for a Cabinet post by President-elect Bill Clinton, worked his way up the ranks to become executive director of the Washington headquarters of the Disabled American Veterans.

In Vietnam he suffered a shattered right arm as he advanced with his unit through a rice paddy near Da Nang early in the war. As a result, he now wears a brace on that arm and extends his left arm for handshakes.

Since his discharge in 1966, he has spent his life in the bureaucratic trenches as an advocate for other wounded comrades-in-arms. In that capacity, he worked both with the White House and Congress, doing his job for the DAV and earning accolades along the way.

Rep. G. V. (Sonny) Montgomery (D-Miss.), chairman of the House Veterans' Affairs Committee, reacted to Brown's appointment with these words: "Excellent. The best possible choice to lead the VA in these crucial times."

Commander-in-chief John M. Carney of the Veterans of Foreign Wars was almost as enthusiastic, saying: "Whether fighting side by side with his fellow Marines in Vietnam or fighting for his fellow veterans in Congress, Jesse Brown has a long and distinguished record of service to his country."

The Cabinet post is vacant now because the former secretary, Edward J. Derwinski, was ousted during the presidential campaign for angering veterans' organizations by his tendency to be too abrupt.

Brown, apparently alluding to his predecessor, declared: "I will be a secretary \o7 for \f7 veterans affairs, not secretary \o7 of \f7 veterans affairs."

He then proceeded to outline an activist credo as he prepares to serve 27 million Americans who have served in the armed forces.

"We will move forward aggressively," Brown said. "We will be innovative and we will be pro-active, not reactive."

Brown faces a staggering task. The veterans' health care network, which costs $14 billion a year and is the largest of its kind in the United States, has enormous financial problems.

Clinton has said that the nation can continue to "gradually bleed it dry and let it go broke or restructure the health care network to make it work at lower cost for more people."