THE BUTTON; The Pentagon's Strategic Command and Control System. By Daniel Ford. Simon and Schuster. 270 pp. $16.95.

WHAT IS the general public understanding about our nuclear arsenal and its intended use? Something like the following: That our very large number and many different kinds of nuclear weapons (some deep in holes in the ground in the Midwest, some on airplanes, some in the sea on submarines) are there to enable the president to respond appropriately to any kind of Soviet attack, either conventional or nuclear, against the United States itself or against its allies. That the president is the only one authorized to release nuclear weapons for use, and helping him arrive at such a fateful decision is a network of early warning sensors and communications that is the latest word in technology. That this network is constantly tested and retested, and is as near to invulnerable to sabotage or Soviet attack as modern technology can make it.

And finally, that our nuclear arsenal has been carefully crafted over the years so that the president need never initiate Armageddon, but instead can engage in a slow escalation of matching nuclear exchanges with the Soviet Union, always with an eye to permitting a negotiated settlement of the war at the earliest possible moment.

In his fine example of responsible and painstaking investigative reporting, Daniel Ford lets us know that none of the above is true. Relentlessly -- and also, it must be said, somewhat repetitively -- he piles up an enormous volume of unglamorous but crucial detail about the state of the U.S. system of nuclear command, control and communications (C3/8, pronounced "See cubed"). The very redundancy of the details, some of which are fascinating, inexorably leads to a soberng list of conclusions from which emerges a disturbing picture of the actual, de facto nuclear policy under which the U.S. is operating today. Some of Ford's conclusions:

The U.S. C3/8 system is obsolete, unreliable, vulnerable to sabotage, dependent (at the level of 94 percent) on commercial telephone lines to transmit crucial messages and totally vulnerable to Soviet preemption.

The early-warning system on which the country relies for notice of Soviet attack is only partly alert at any time; it cannot provide information about the size or exact destination of an attack, and its links to the Pentagon and the president are unreliable, unduly complex and under-rehearsed. In an unsettling incident recounted at the beginning of the book, Ford describes the inability of the brigadier general at NORAD (North American Aerospace Defense Command) in charge of combat operations, the man who is supposed to alert the president in case of Soviet attack, to get through to the White House in a demonstration of the 24-hour connecting phone link (NORAD fact sheet: "When we pick up a telephone, we expect to talk to someone at the other end -- right now."). Later, the general explains to Ford that he has been in charge of NORAD combat operations for only a few months, and "I didn't know that I had to dial 'O' to get the operator."

The U.S. military, who are aware of the grievous inadequacy of our C3/8 systems, are determined to "go first" during a deepening crisis with the Soviet Union, for fear that if they wait, they will not be able to launch their nuclear weapons.

As a consequence, even though the technologies to improve the reliability and robustness of our C3/8 system exist, the military are not interested in making these improvements because they do not consider them necessary: the present system is good enough to launch an all-out preemptive strike.

Precautions aimed at avoiding paralysis of our nuclear forces in case the president should be unavailable mean that a number of military officers have access to the codes needed to launch our nuclear weapons. In fact it is not just the president who can release nuclear Armageddon.

WHAT EMERGES from Ford's investigation is that the Pentagon is "deliberately incompetent" when it comes to C3/8 not because the military are hoping to launch an all-out attack, but because they think the probability of war is small. If, however, they are proven wrong and a war appears unavoidable, they plan to launch the entire nuclear arsenal. Actual military planning for nuclear weapons has had no connection to the nation's "declaratory policy" for some years -- perhaps not since John Foster Dulles. While the so-called "nuclear theologians" spun arcane but intellectually dazzling scenarios for nuclear weapons use within their closed community, and successive secretaries of defense grandiloquently exhorted the Congress to provide funding for new nuclear weapns capable of "surgical strikes" or of fighting and winning a nuclear war, the military have been preparing all along for a preemptive attack.

"In a real situation," a former Pentagon official is quoted as saying, "you don't compare going first to going second. You compare going first with not going at all. If you are going to get into nuclear war, that's big time. When you go, go. Do it. Finish the job." Mr. Ford adds, "By sticking with a relatively crude command and control system, the military has set its own nuclear weapons policy in concrete. The existing command system, despite its shoddiness in many respects, is good enough for the application of brute force they have in mind."

Further, their plan calls for immediate elimination of the Soviet leadership -- a strategy known vividly as "decapitation." This course, most obviously, removes the very people with whom any settlement could be negotiated. But even more important, since control of Soviet nuclear weapons is closely held by the political leadership, such an intention almost demands that the Soviet Union launch first, for fear of losing the ability to do so.

The determination of the U.S. military to include decapitation in its large-scale attack is well-documented. A memo written in 1980 by General Bruce K. Holloway, former commander-in-chief of the Strategic Air Command, said, "Degradation of the overall political and military control apparatus must be the primary targeting objective . . . it assumes the importance of absolute priority planning. Striking first would offer a tremendous advantage and would emphasize degrading the highest political and military control to the greatest possible degree." Or as Colin Gray, a defense consultant who strongly influences the Reagan administration's nuclear strategy, has put it, publicly and gruesomely, "Cut off the head of the Soviet chicken."

In a building crisis, the Soviet response to such a declared strategy is easy to imagine. Though they have an extensive network of command and control bunkers to protect their leadership, and though their C3/8 system is more redundant than ours, and therefore presumably more resistant to degradation, it is safe to assume that they must be at least as concerned as our military about their ability to launch their nuclear arsenal after an attack. This would naturally lead them also to the conviction that they must go first. Here we have the classical recipe for what is known as "crisis instability": Both adversaries believe their strategic nuclear weapons are vulnerable; therefore, in a crisis, each would perceive an advantage in launching first. This is exactly the opposite of strategic stability, a highly desirable situation in which the outcome of a nuclear exchange would confer no benefit on the side that started first, and therefore, in a crisis there would be no incentive for either side to do so.

Will the $18 billion five-year plan of the Reagan administration to improve strategic C3/8 systems remedy the vulnerability of our system and contribute to strategic stability? Ford argues persuasively that it will not. First, he says, the Pentagon bureaucracies responsible for the implementation of the plan tend to be "technologically illiterate" and motivated by parochial interservice rivalries, as well as, in some cases, by consideration of personal gain. As Ford delicately puts it, "Human nature and the incentives to which large bureaucracies respond do not guarantee that what best serves the national defense becomes the deciding factor in allocating Pentagon resources." A second, and more powerful, reason is that the military is set upon the plan to strike first, and therefore they do not believe that $18 billion should be spent on improving C3/8 to support the management of the strategic arsenal.

Ford has done the nation a great favor with this book. He has revealed in convincing detail that the public perception of nuclear weapons firmly controlled by the president and intended to be used only in retaliation to a Soviet attack is, in his words, "a piece of contemporary folklore." May the book awaken us from our state of ignorant complacency about the management and the intended use of our nuclear arsenal, and even suggest some new directions that public pressure might usefully take.