U.S.military dominance goes largely unquestioned. No army can hold a battlefield against our troops. No planes can ground our Air Force. No enemy ships can challenge our naval dominance.

Whales, though, are a different story.

This month, the U.S. Navy is leading a massive international war game in the Pacific Ocean. More than 40 vessels from eight nations are teaming up to search the seas for enemy submarines.

But they won't be searching the entire ocean.

Environmentalists argued that the Navy's mid-frequency, high-intensity sonar -- the best system for locating enemy submarines -- bothers marine life. Federal Judge Florence-Marie Cooper agreed, saying "considerable convincing scientific evidence" shows naval sonar "can kill, injure and disturb many marine species." So she recently issued a temporary restraining order blocking the Navy's sonar exercises.

To allow the naval exercise to go forward, the Navy and environmental groups reached a compromise: Vessels won't use their sonar within 25 miles of the Northwestern Hawaiian Islands Marine National Monument, a nature preserve President Bush recently set aside.

Next time we should just draw up a map for our enemies: Operate here, and we guarantee we won't do anything about it.

This all happened because, during exercises two years ago, 150 whales came too close to shore. Environmentalists claim those whales beached themselves because of the naval sonar tests. In the end, though, only one whale died -- the other 149 were escorted back to sea.

This year's tests are even more important, because enemy subs are a real and potentially growing threat. The Chinese, for example, are adding subs as quickly as they can.

In years to come they plan to launch a dozen boats built by Russia, while Chinese shipyards are turning out 2.5 new subs each year. Just last year Defense Secretary Donald Rumsfeld warned the Chinese might have more subs than our Navy does within a decade. Many of these boats are quiet -- able to operate on batteries for weeks at a time. In fact, the Navy says at least 40 countries have submarines that may be quiet enough to escape traditional sonar systems. That's why it needs to test its high-powered systems.

Plus, a recent Navy paper says, "Many submarines are commercially available and can be easily found on the Internet, ostensibly for the purpose of tourism." But the would-be Jacques Cousteaus renting these boats could easily turn out to be bad guys. "It is not a broad stretch to imagine one in the hands of a fanatical terrorist organization," the paper warns.

Historically speaking, military maneuvers and environmental damage go hand in hand. Sherman marched through Georgia, burning everything in his path. By 1945 Allied bombers had reduced Germany and Japan to rubble. In Vietnam the military used napalm to destroy huge swaths of jungle.

Things are a bit different today. We're probably the only country in the world with a navy that includes a "director of environmental readiness." Our desire to keep whales healthy shows we care about our environment.

But should our military be so green that its readiness is compromised? The fact is, it must be able to prepare for any eventuality. Yes, make every reasonable effort to help protect whales, but not at the expense of national security.

Americans have enjoyed total battlefield dominance for so long that some seem to have forgotten that it must be earned -- every day. It shouldn't be given away to protect whales (or any other animals). If we forget that, someday one of our enemies -- one who won't care how many whales it kills as long as plenty of Americans die, too -- will eventually remind us.

Edwin Feulner is president of The Heritage Foundation (heritage.org), a Washington-based public policy research institute and co-author of the new book Getting America Right.