Out here on and beneath the Great Plains -- the Breadbasket of the Soviet Union -- resides part of the U.S. deterrent, the Strategic Air Command. Long ago someone -- someone too clever by half -- saddled SAC with the slogan "Peace Is Our Profession," which was like putting chintz curtains in a tank. Deterrence is a product of a national readiness -- material and moral -- to wage war.

SAC is at the center of an ongoing calculation, complex but straightforward, of what the U.S. strategic arsenal must include in order to absorb a Soviet first strike and remain able to inflict unacceptable damage on the Soviet Union. One difficult assessment is: What does the Soviet elite consider unacceptable?

The United States can target strategic systems, military support systems, the industrial base and the leadership elite. This last is crucial because the Soviets have been rapidly increasing investment in dispersed and hardened shelters to protect many thousands of the Soviet elite in a nuclear war. The inescapable conclusion is that those who make and implement Soviet policy regard shelters as war-fighting assets and regard nuclear war as survivable and winnable.

In commemorations of the end of World War II, the great fact of the last 40 years has been too little remarked. It is: never in history has there been a frittering away of military advantage comparable to that by the United States, relative to the Soviet Union, since 1945.

SAC headquarters is a place to see, in the mind's eye, the change: imagine how a SAC commander of just 20 years ago would react to the intelligence data that pours in for today's commander. Everywhere that U.S. technical means of intelligence-gathering look in the Soviet Union, menacing military activity is noted.

Soviet planners know that in any crisis, they will shoot first. And the task confronting Soviet targeters is simpler. There are many fewer targets in the United States than in the Soviet Union. The Soviet Union is larger and its targets are increasingly hardened, dispersed and mobile. A significant and growing fraction of the Soviet target base is mobile. The Soviet Union could hold nearly half its strategic forces in reserve and with the other half do damage to the United States comparable to what the United States would do using all its forces against the Soviet Union.

The good news here is that on June 29, 30 years to the day after the first B52 was delivered to SAC, the first B1 will be delivered. The last B52 was delivered 23 years ago, so the youngest B52 is older than some members of its crew. The B1 was killed by Jimmy Carter and resurrected by Ronald Reagan and is a suitable symbol of the difference Reagan has made for the military.

But even -- in some ways, especially -- in an era of high-tech weapons such as the B1, the most important variables in the military organization are men and women. The crucial variable of morale may be about to vary adversely, because of a political climate to which Reagan policies have contributed. By shrinking the government's revenue base, and making politically impossible even a small restoration of the base through a tax increase, Reagan has forced Congress to choose between cutting middle-class domestic programs and cutting the military. The result? A nibble from Amtrak subsidies, a large bite from the shield of liberty.

Many of SAC's key personnel -- middle-rank men and women operating computers and other complex systems -- could triple their incomes by entering the private sector. That so many stay in uniform is attributable to two things. One is a system of military pensions that is a form of deferred compensation. The other is high morale that results from believing the country appreciates what they are doing. This is jeopardized by the drumbeat of criticism of the military, and especially of pensions.

Political rhetoric encourages the public to believe the budget can be balanced by curbing "runaway" military spending and that the key is to cut expensive strategic systems, and eliminate $800 screwdrivers and "scandalous" pensions. But strategic systems are a small slice of the defense budget, and Congress mislays more money in a morning than is spent on overpriced screwdrivers. So, pensions become the target of opportunity.

Of course, one way to run up the cost of defending the country is to defend Amtrak subsidies by attacking the material and moral incentives that keep trained personnel in the services. One hopes, but not confidently, that the men and women who maintain America's shield are too busy doing so to notice some of the rubbish spoken by persons whose liberty to speak rubbish is the result of the shield.