The test of a new Chinese stealth fighter, the J-20, certainly is something to fuss about. For awhile it's been reported that the Chinese were developing a variety of stealth aircraft, but this is the first time that Beijing has gone public with its stealth program. And it did so just as Secretary of Defense Robert Gates was visiting China.

The plane itself may or may not be very stealthy. No one can really tell until its radar cross section is revealed through a stealth measurement system, or if a search radar identifies it—or fails to do so. It is a big plane, closer to the size of a medium bomber than a fighter, but it appears to be very maneuverable, more like a fighter than a bomber.

The J-20 is being compared to the old American F-111 medium bomber in terms of both its range and its mission. The F-111's range was over four thousand nautical miles. More important than range is the combat radius—the furthest distance a plane can fly and then return back to its base. The combat radius for the F-111 was about one thousand four hundred nautical miles, a few hundred miles short of the shortest distance between China and Guam, which is becoming an increasingly important American military facility in the western Pacific. But even combat radius does not accurately foretell how far a plane can fly on a mission. The true radius depends on the combat load and flight profile. A flight profile that enables the plane to evade air defenses (from surface ships, for example) will have a much reduced combat radius. Should China develop a viable aerial refueling capability, the combat radius of its fighters could increase—assuming that they can do so without interference from hostile aircraft—from American aircraft carriers, or, for that matter, Taiwan or Japan.

Regardless of the jet’s actual capabilities, which will always be subject to guesstimates unless one falls into Western hands, there can be little doubt that the J-20 is yet another indicator of China’s ongoing effort to develop an outward-looking force posture. China continues to develop a military that is designed to assert its influence throughout East Asia. China’s extended-range missile program, its plan to build an aircraft carrier, and its efforts in space are all of a piece with the J-20. China’s military no longer focuses primarily on the country’s interior, though the J-20 could provide a potent capability against any insurrection in, for example, the Muslim majority Xinjiang province. Its naval and air capability is not solely aimed against the United States. The combat radius of a J-20 may not suffice to reach Guam. But it certainly could reach most of northwest India from bases in the Chinese interior, and depending on its flight profile, could reach New Delhi as well.

Mr. Gates has begun to sound warnings about China in a far more urgent manner than he did in past years. Perhaps he is doing so to ensure some protection for his defense budget. More likely, however, he is building a momentum for procurement of major U.S. air, naval and space systems that he hopes his successor will maintain.

Both the Navy and the Air Force did not benefit as much from the increases of the first decade of this century as did the Army. The size of the fleet has shrunk to half of what it was as recently as twenty years ago. To ensure America’s dominance in air, sea and space—in other words, to ensure that whatever China may develop, it will have little incentive to confront the United States militarily—will require sums that the Pentagon may not have at its disposal, unless it cuts more deeply into other programs. That is an unpalatable prospect for the Pentagon, but it is a challenge that must be confronted, if the United States wishes to maintain sufficient military superiority over China to deter Beijing from undertaking a military adventure it would later regret.