07/09/2013 05:21 pm ET Updated Sep 08, 2013

Sizing U.S. Military Forces: How Much Is Enough?

Secretary of Defense Chuck Hagel is now established in his new position. He is facing some critical personnel issues including horrible rape and suicide rates. He cannot ignore these systemic issues, but neither can he ignore his responsibility to manage the postwar drawdown of military forces.

There's nothing new about the situation Hagel faces. As wars end, we draw down the force. A 50 percent drawdown took place after the Vietnam War without adequate planning, resulting in what was called the "hollow force." At the end of the Cold War, the Bush 41 administration reduced the force by nearly 20 percent in four years and fell through its own Base Force floor. The Clinton administration reduced the force by nearly 19 percent in eight years and fell through its own Bottom Up Review floor. While drawing down the force both Bush and Clinton increased the use of force. Bush 43 further increased the use of the smaller force; force levels remained flat but were augmented with private contractors to an unprecedented degree. Pressure on the force was intense. Under the Obama administration, the use of force has declined, and defense budgets have been reduced the last three cycles. We know it will be smaller, but how much military power is enough?

Politicians and pundits tend to adopt a position on how much is enough and argue their position in simplistic sound bites and talking points. But there is a deeper logic -- a theory -- underlying their arguments that's worth examination. The word "theory" is used as a dismissive label by many -- e.g., "it's just a theory." But prominent theories in international relations rest on centuries, even millennia, of hard evidence.

The security dilemma is a classic component of international relations theory. Having too little power invites aggression from an opportunistic neighbor. Too much power also invites aggression. A state's excess power can appear threatening to others, and rising tensions may lead to war. But having enough power deters risky aggression. How much is enough?

One answer is just enough to defend the state against aggression -- defensive power. Another answer is enough to defend the state plus enough to tip the scales abroad, possibly in concert with a coalition of those who share our interests -- balancing power. And a third answer is enough power to defend the state plus enough to dominate in any conflict in the world and against any coalition that might form in opposition -- preponderant power. Preponderance is clearly the most expensive answer to the "how much is enough" question. The preferred force posture follows from a preferred theory, but neither is publicly debated.

The public debate, what little there is, will be about the size of the Defense budget. Important, but not terribly informative. The budget is a measure of input but doesn't say much about the military force that is the output of the process. Should we be investing in defensive, balancing, or preponderant power?

Two theories underlie the discussion. For convenience, we might call them the provocative weakness theory and the provocative power theory.

The provocative power theory is the well-established theory that states balance against power (called balance of power theory in the specialized literature). When one state assembles more power than is necessary to defend itself, other states will see the excess power as offensive and threatening -- provocative power. The threatened states can gamble with their survival or they can take action: initiate preventive war before the rising power achieves predominance, enter into a costly arms race to maintain the balance, or aggregate power through alliance to balance against the threatening state. Having too much power leads to a spiraling power competition often paving the road to war. Holding to this theory leads one to answer the how-much-is-enough question with balancing power or even defensive power.

A fairly new theory, the provocative weakness theory, proposes that it's not too little or too much power that invites aggression; instead, acts of weakness invite aggression. Maintaining a reputation for quick and decisive military force is a vital interest justifying war ("Credibility"). Hardliners believe that diplomacy, negotiation, and willingness to talk to enemies are signs of weakness, but a rapid and decisive military response shows strength. Attempts to engage enemies diplomatically or negotiate arms control agreements raise alarm of Hitler, Chamberlain, and appeasement at Munich. Calling someone "weak on defense" is an effective political slur. (Forty Years War does an excellent job of showing the role this theory has played.)

The provocative weakness theory is publicly presented under the benign rubric of "peace through strength" and "strong on defense." In closed circles, hardliners have argued explicitly for a militarized foreign policy. And implementing a militarized foreign policy requires a large standing military to police the world. The provocative weakness theory leads to a strategy requiring both the development of a large force and the aggressive use of the force.

Those who favor defensive power and balancing power argue that an aggressive, militarized foreign policy induces opposition and further distances the U.S. from its friends, creates enemies, and damages the economy upon which national security ultimately rests. Hardliners argue that only a preponderance of U.S. military power and its aggressive use can assure world peace and that the U.S. economy can support it.

There is a great deal of historical evidence going back to the Peloponnesian War on the side of balancing power. But balancing requires deft handling and can fail to prevent war, and history includes examples of miscalculating the balance. There is also historical evidence on preponderance of power. It is the story of Roman, Spanish, English, and Soviet overextension. Preponderance of power creates more opposition and a vicious cycle where greater acquisition and exercise of power leads to greater opposition requiring, in turn, acquisition of more power.

In spite of the post-Cold War drawdowns, the U.S. still holds a preponderance of power. Today's base Defense budget in constant dollars is larger than budgets dating back to the beginning of the Cold War. U.S. Defense expenditures exceed the combined expenditures of the next dozen or more countries, including China.

Without vision and strong management from Secretary Hagel, budget reductions will be shared equally across the four services and across weapon acquisition programs. As with past reductions, insiders are calling for reductions in the bloated Pentagon staffs and inefficiencies squeezed out of the byzantine weapon acquisition process. Not bad ideas, but they don't answer the question. The question remains, how much is enough: defensive, balancing, or preponderant power?

Where do you stand on the issue? Your friends? Your elected representatives?

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