Paul Kennedy

What does a nation do when it faces plenty of external challenges and plenty of potential threats -- and has interests and obligations across the world?

Well, perhaps it should think harder and more coherently than it might previously have been doing. Perhaps it needs to breathe in, swallow hard and make some difficult decisions. Perhaps it needs to be rather ruthless, simply in order to maintain its basic interests. Perhaps it -- and the country I am writing about is clearly the United States in today's troubled world -- needs to re-assess its global position, and its global future.

A few days ago, the Pentagon presented its congressionally-mandated Quadrennial Defense Review, a grand survey by the brightest of the U.S.'s defense planners, of where the country's chief security challenges probably lie; in consequence, it suggests decisions that have to be made regarding both regional priorities and weapons spending.

Reading that document, it becomes obvious that the White House and Pentagon are struggling with age-old dilemmas and, most particularly, with defense-spending priorities. And some serious decisions are being made. To his credit, the able Secretary of Defense Robert Gates is insisting on closing down various expensive but dubious weapons systems, or at least reducing them in size, notably the Air Force's most expensive fighter, the F-22 Raptor.

On the other hand, it is pushing the annual defense budget up to well over $700 billion, and sending more troops to Afghanistan. Supporters of enhanced defense spending have many things to justify this further expansion.

For a while (or so they hope) the Afghan war will have to be more, not less expensive. The whole Middle East is fragile. Al-Qaida is spreading though southern Arabia and into Africa. Putin's regime is up to no good in its neighboring states. Iran is dangerous. North Korea is in the hands of a lunatic. Weapons of mass destruction are spreading. Collapsed states, brought down by poverty, environmental stress and ethnic violence, are becoming the new bolt-holes for terrorists. Then there is the challenge of China's steadily rising military and economic capacities, and the tilting of the Asia-Pacific strategic balance.

Now add to this the growing drumbeat of questions about the fragile international economy, and perhaps more specifically about the astronomical American trade deficits, together with unprecedented high federal deficits that are forecast to stretch out to the far horizon. No Great Power can survive at the top if it cannot pay its way, which is why an increasing number of Americans, and pro-Americans abroad, are concerned. Can the United States afford -- and do -- all the things it appears intent on doing, both in regard to its domestic needs and its overseas requirements?

It is in this context that President Obama, Secretary of Defense Gates, and the U.S. chiefs of staff -- and their successors, and successors' successors, for these problems are not going to go away -- will have to attempt to reach some hard conclusions about future defense spending, and get the agreement of the majority of the members of Congress, who bleat incessantly about unsustainable federal deficits but fight to the death to prevent cuts to weapons production and military bases in their own constituency.

To an outside observer (in other words, to someone who hasn't personally to make these hard choices), the temptation to point to some lessons from military and naval history are irresistible. One such "lesson" might be the following: that weapons systems and structures that give decision-makers the greater flexibility are preferable, especially in pinched economic times, compared with those designed for a more limited number of war scenarios.

In the case of the Roman Empire, the most ubiquitous instrument was the legionnaire himself: the soldier who could fight from the borders of Scotland to the borders of Persia, build bridges, create siege engines, and put together identical fortress camps over most of the Western/Mediterranean world.

In the age of Nelson's navy, the "jack of all trades" was the swift, midsized frigate; it was the "eyes" of the battle fleet, the speedy transporter of dispatches or other urgent items, the vessel that could operate in the farthest regions of the world.

During World War Two, the Royal Air Force's most useful plane was the versatile twin-engined Mosquito -- it could fly at extremely high altitudes and couldn't be caught, it could fly at low levels against enemy tanks and ships, it could (if converted) carry a greater bomb load than a Flying Fortress; it was a night fighter, a Pathfinder and a photo-reconnaissance plane, all rolled into one.

What does this suggest about the state of President Obama's armed forces today, and American capacities and power? Some weapons systems are more one-dimensional than others. For example, main battle tanks and heavy artillery, constructed for the possibility of a major land war against the Red Army, are hopeless for fighting in the mountains of Afghanistan, just as they were in the paddy fields of Vietnam.

Ground forces, like the Marines or Army Special Forces, can go pretty well everywhere. Helicopters can be deployed everywhere, except where lousy weather prevails. The Navy's attack submarines are pretty ubiquitous (so why haven't we sent one to scare off the Somali pirates?) Possessing a dozen enormous aircraft carriers looks excessive, given America's colossal naval predominance over all other navies.

Now the reader might properly ask: "Surely the first thing that has to be done is to determine which threats, which enemies, lie out there, and then choose your weapons accordingly?" A good point, because it would also mean that the American leadership would at last have to choose which weapons and force structures are essential to meet the defined dangers, and which are not.

Which brings us back to the point made above. Since the White House, Pentagon, State Department and the Congress don't want to make such a determination, we are going to be left with second-order decisions like scrapping a few weapons systems that seem not to work/have become too expensive.

Thus, what should be done -- a real ordering of strategic priorities and a much more significant cut in our panoply of weapons systems -- will not be done; and the "eggs" of U.S. defense allocations will be continue to be distributed into a very large number of "baskets."

That is not a happy solution for a number-one power in a century of so many and different threats, but right now it may be the only route available. How long, one wonders, can this go on?