ABOARD THE USS DWIGHT D. EISENHOWER IN THE RED SEA, AUG. 19 -- At the shout of "Campfire Bravo!" ammunition teams roll carts piled with missiles and other munitions down "bomb row" to waiting fighter jets and bombers perched on the deck of this massive aircraft carrier.

Beneath the flight deck, the hottest movie running on the ship's closed-circuit television system -- with showings three and four times daily -- is "Donning and Doffing," a sailor's video guide to using and wearing personal chemical-warfare protection gear. Across the Arabian Peninsula in the Persian Gulf, the crew of the destroyer USS David R. Ray has been ordered to full battle-station alert nearly five times a day for the last week.

In the 2 1/2 weeks since Iraqi troops invaded neighboring Kuwait, conditions on U.S. warships in the Middle East have changed dramatically from routine patrols to combat-zone alert levels and near-wartime tensions, according to officers and seamen interviewed on five U.S. ships operating in the Red Sea and the Persian Gulf.

"Things have changed drastically," said one sailor aboard the Ray. "They've gotten really tense." And since Thursday, when President Bush authorized American warships to use force if necessary to enforce a international trade sanctions against Iraq and occupied Kuwait by stopping cargo vessels, the alert levels have escalated.

The Navy is organizing a new command structure to control the growing number of ships and Marine units being diverted to the Middle East. The new U.S. Naval Forces Command will be headed by Vice Adm. Henry H. Mauz Jr., who will be assisted by two additional admirals and a Marine lieutenant general, according to naval authorities in the region.

Most ships have been ordered to train and arm board-and-search teams to be used for inspecting cargo vessels as part of the interdiction effort. And as a safeguard against the possibility of Iraqi retaliation, masks and coveralls for protection against chemical weapons have been pulled out of storage and issued to each officer and seaman aboard all U.S. ships in the region.

"We're all kind of shaky," said a Missouri sailor assigned to the Eisenhower.

When a small group of reporters boarded the guided-missile cruiser USS Ticonderoga in the Red Sea just an hour after the frigate USS Reid fired six warning shots across the bow of an Iraqi tanker Saturday in the Gulf of Oman, an officer gave the journalists quick instructions for using the protective gear "if, for some reason, something terrible happens."

Three years ago, when the U.S. Navy was providing escorts for U.S.-flagged Kuwaiti tankers traveling in the Persian Gulf, the Pentagon assembled an armada of about 40 ships in the region. But after a cease-fire was declared in the Iran-Iraq war in 1988, the escort mission was discontinued and the number of U.S. ships in the gulf dwindled to about a half-dozen.

The once dangerous gulf duty became little more than routine, notable only because there are so few liberty ports in the region. Just weeks before Iraq invaded Kuwait, the Navy believed the gulf had become so benign that detachments trained to use the shoulder-fired Stinger anti-aircraft missile were eliminated from many ships, including the Ray.

Now the Stinger detachments are back on round-the-clock shifts. Aboard the Eisenhower, the supervisor of the combat information center said: "We have extra people on watch. We don't take anything for granted." Officials on one ship in the gulf said their vessel is ordered to battle stations each time intelligence reports indicate an Iraqi plane is being loaded with weapons.

Aboard the Eisenhower, F-14 Tomcat and F/A-18 Hornet fighters and A-6 Intruder ground-attack aircraft sit on the decks, loaded at virtually their full capacity of missiles and bombs. The Eisenhower's crew was within a few weeks of returning to the United States after a leisurely cruise through the Mediterranean Sea, including liberty stops along the Riviera, when it was ordered to head for the Red Sea.

Now, crew members aboard the Eisenhower and other ships have begun receiving a flood of letters from worried families reading headlines in the United States.

"I've gotten five letters from my mother in the last five days," said a sailor assigned to the Ticonderoga.

But the current crisis has spawned a few light moments for the harried seamen. When nine crew members on liberty from the Ray stopped in a Mexican restaurant in Manama, Bahrain, last weekend, a member of the island nation's royal family who also was dining there walked over to their table and announced: "The royal family wants to thank you for your present efforts to help us," a sailor recalled. "You please eat and drink as much as you can -- for free, on us."

The table of sailors proceeded to drain four pitchers of margaritas.