The nomination of Army Gen. John W. Vessey Jr. to be the next chairman of the Joint Chiefs of Staff presents a mixture of tradition and change.
General Vessey follows other notable Army men -- Omar Bradley, Lyman Lemnitzer, Maxwell Taylor, and Earle Wheeler -- who have been the president's chief military adviser. But he is the first Army officer to fill this senior post without having graduated from West Point, and he is only the second Joint Chiefs chairman not to have been his service's chief of staff.
If approved by the Senate (as is expected), Vessey also could become one of the most powerful chairman since the Joint Chiefs was formally organized under the National Security Act of 1947. The man he would succeed -- Air Force Gen. David C. Jones -- recently proposed that the Joint Chiefs chairman be given greater authority to reduce interservice rivalries.
General Jones's recommendations eventually will take form as specific legislation; so far they have been receiving generally favorable response.
The Joint Chiefs of Staff (JCS) was designed to provide the president and secretary of defense with broad advice on strategic and logistic planning, budget matters, and military force levels. There are five members, one each representing the Army, Navy, Air Force, and Marine Corps, plus a chief.
The basic JCS problem is structural, since the four service members also are the chiefs of their own branch.
''The services have an understandable desire to promote organizational interests, to preserve their sovereignty, and to conserve hard-won perogatives, '' Jones said recently.
What this means, he added, is that JCS decisions reflect a watered-down committee consensus ''in which each service has almost a de facto veto on every issue'' rather than firm advice that is free of ''an intramural scramble for resources.''
Among the recommendations from Jones for improving JCS structure and operations:
* No longer allow the staffs of the individual services to review and pass judgment on joint policy proposals.
* Allow the JCS chairman to assign and promote officers who have had interservice jobs, thereby encouraging broad military experience.
* Give the JCS chairman greater authority in advising civilian executive officials, as well as in dealing directly with the commanders of unified or multiservice US forces.
Congress will take up these proposals later this year, and it is expected that there will be some opposition from the individual services as well as from those concerned that a ''general staff'' on the German model could result.
Into all of this steps Vessey, a combat veteran and ''soldier's soldier'' (as Mr. Reagan described him), who received a battlefield commission as an artillery sergeant at Anzio.
His selection came as a surprise to many at the Pentagon and on Capitol Hill. His name had not been prominently mentioned as a successor to Jones, who must retire as JCS chief after two consecutive two-year terms.
But his nomination is in line with what might have been expected from Reagan.
He was passed over by Jimmy Carter to be Army Chief of Staff because he opposed the SALT II treaty and the Carter plan (later abandoned) to reduce the US military force in Korea. Yet, rather than retire, he stayed on to serve as Army vice-staff chief under a man he had once commanded. The President admires this holding to principle and dedication.
Vessey, an Army man with much field experience, also is seen as balancing the sharp naval buildup planned for by the Reagan administration and the tendency in recent years for officers to be promoted for their ''managerial'' rather than ''leadership'' qualities.