Washington — The 1984 Pentagon budget dramatizes the sharp Reagan imprint on domestic politics, allied relations, and superpower confrontation. This is the year when Congress, if it is to curb the Defense Department buildup, must turn its rhetoric into results. It is a time when the Atlantic alliance will act on key decisions, with the United States military budget a crucial factor. And it brings with it the prospect of major weapons deployment that could influence American strategic posture and the likelihood of successful deterrence - or nuclear war - for decades to come.
On the homefront, the clear trends in administration priorities were never more evident. While just about all the rest of federal spending is to feel real cuts, military outlays under the Reagan scenario will enjoy real increases. Fully three-quarters of the total boost in the national budget is directed to the armed services.
The halls of Congress ring with predictions of a ''donnybrook'' over military spending. But after two years of Reagan successes, skeptics are siding with the President in their predictions about the outcome. Congress gave the Pentagon 95 percent of what it wanted this year, and 99 percent the year before. Not a single major weapons system has been killed, despite choruses of criticism.
For 1984, the administration is seeking a 10 percent increase (not counting inflation) in defense outlays - from $216 billion to $239 billion. In budget authority (a more accurate measure which includes money obligated for future spending), the increase would be from $249 billion to $274 billion.
Emphasized in the military budget are strategic nuclear weapons, where funding obligations would rise 30 percent over this year. By comparison, spending for general purpose forces would go up less than 5 percent. This reflects two things: the administration emphasis on upgrading land- and sea-based missiles as well as other aspects of the strategic triad; and the larger bills now coming due for earlier decisions on systems like the MX and Trident missiles (up 89 percent and 305 percent, respectively).
Like Vice-President George Bush's current trip to Europe, Defense Secretary Caspar Weinberger's message to Congress accompanying the budget was designed to soothe public fears about an overly aggressive defense posture. It affirms that the US would not start a war, it doesn't intend to fight a ''limited nuclear war ,'' and it does not believe nuclear war can be won.
But it also continues the Reagan-Weinberger theme that the US must beef up defenses that have been ''neglected'' in recent years while the Soviet Union's continued to grow. ''The global military balance has been shifting steadily against us,'' warns the defense secretary. ''Local threats against our allies and friends have increased as well.''
And it takes pains to illustrate that all this does not mark any shift from earlier American positions. For example, it quotes from defense posture statements going back two decades to show that the strategy of ''flexible response'' (conventional or nuclear) to attack in Europe has not changed.
In line with this stand, the administration will (through a supplemental appropriation) try to make up what it lost this year in items important to NATO. This includes funds for the Pershing II intermediate-range and cruise missiles, as well as the prepositioning of American military supplies in Europe.
Other Pentagon budget highlights:
* The most significant conventional force expansion goes to the Navy. This includes more money for the two new nuclear aircraft carriers approved by Congress and production of attack submarines at twice the rate envisioned by the Carter administration.
* Active duty military personnel will increase by 37,300 to 2,164,700. To make up for the military and civilian pay freezes planned for 1984, the administration will seek a raise for uniformed personnel the following year.
* Because of cost considerations, purchase of some major conventional weapons is being slowed down and stretched out. This includes the M-1 tank, and the F-14 , F-15, and F/A-18 tactical jet aircraft.
* The administration wants to buy 10 more B-1 bombers, up from 7 this year, and plans to buy 34 next year. Ballistic missile defense systems (needed to protect US intercontinental ballistic missiles, including the MX) would increase from $519 million in '83 to $709 million in 1984 and $1.6 billion in '85.
Secretary Weinberger this week will make three appearances before congressional committees to explain a philosophical position and budget thrust that has remained virtually unchanged since the Reagan team took over. Some are saying that changes now are inevitable, and that perhaps Weinberger himself will have to step down. The record so far indicates otherwise.