"It's been like trading in an old Hudson for a brand new Cadillac," beamed Lt. Col. Douglas J. Middleton as he contemplated the switch from older projectiles in his arsenal to the 36 fleet and accurate Pershing II nuclear-armed missiles now under his command.

Middleton, a battalion leader in the U.S. Army's 56th Field Artillery Brigade that operates the missiles here, has other reasons to be happy about the presence of his much discussed new weaponry.

After years of anguished prophecies that its deployment would trigger a nervous breakdown of East-West relations, or even instant Armageddon, the Pershing II has become an accepted fact of life in this rustic, hilly region less than an hour's drive from Stuttgart.

The antimissile demonstrations in West Germany have lost their vigor, as widespread public opposition apparently has turned to acceptance of the new Pershings. U.S. soldiers no longer have to pull guard duty every third day, as they did at the peak of the protests last autumn.

The local population has focused its wrath on the last few diehards who trample farmlands while conducting a quixotic crusade to thwart exercises with the new missiles. Lucrative U.S. Army construction contracts, worth nearly $6 million here this year and twice that much next year, may have appeased much of the home-grown opposition.

The slackening of the protests has generated a confident air of victory and vindication throughout the battered barracks of the Bismarck Caserne that serves as headquarters for the Pershing battalion here.

"I'm absolutely amazed how well the soldiers adapted under such difficult circumstances," Middleton said. "For months, they were constantly harassed by people who threw paint, yelled obscene insults, blockaded their trucks -- yet there was not one incident of a soldier losing his cool."

Morale is high among the 1,500 men and women who serve under him, he said, and not only because they weathered the troubling ordeal of the German antimissile campaign. The strong dollar, recent military pay raises and the new buoyancy of American patriotism have enhanced the plight of all U.S. troops overseas.

Several soldiers contended that the difficulties in coping with the protesters could have been eased if the nature of the Pershing II deployments had been explained to the public in better fashion.

"We're talking about replacing older missiles, more prone to accidents, with new ones that are better, safer and more reliable," said Staff Sgt. William D. Parsons, who heads a decontamination unit in the battalion. "If more people realized that, there would have been less fear all around."

The old Pershing IA missiles were discarded when the West German legislature approved deployment of the new missiles last November. The first battery of nine Pershing IIs was declared operational on Dec. 15. Middleton admitted that he was "naked," or left without any missiles, for about three weeks.

Unless an arms control agreement is reached by the United States and the Soviet Union limiting intermediate-range missiles in Europe, 108 Pershing IIs are to be deployed by the 56th Field Artillery Brigade in West Germany, at sites at Heilbronn, Neu Ulm and here, by 1986.

Middleton's is the first of three battalions to be equipped with four full batteries of Pershing IIs. He said his peers are "highly jealous" because the delivery plan already has enabled his troops to conduct field exercises, performed without live warheads.

The officer recalled the artillery school motto, "Move, shoot, communicate," and said that in the present context "it's important to get out on the roads and into the woods and test the thing, because by practicing and innovating, we can improve our survivability." That survivability is in question because the Soviets are assumed to be targeting the static missiles.

"The kids are really excited with this fancy equipment," he added. "It's state-of-the-art stuff." The Pershing II uses the same launcher as the old model, but its greater range -- about 1,000 miles -- through a second stage would enable it to strike targets in the western parts of the Soviet Union.

The missile's most prized advantage, Middleton said, is its accuracy, ensured by a "smart warhead" that flies itself to the target using digital correlation radar.

"That's why the Russians made such a fuss about it," Middleton said. "With the old missile not all targets were at risk because the ballistic guidance system was such that we were not sure we could hit the targets."

"Now they [the Soviets] know: If I aim at it, I'll hit it," Middleton said. "Even if they don't know what I'm targeted at," he added, smiling.

Soldiers handling the Pershing II on test exercises said it is much simpler to operate than its predecessor. The new model only requires two cables to be plugged in before being ready to fire, while the Pershing IA trailed 28 cables off the launcher.

The new missile is moved around on the back of a eight-wheel-drive diesel truck, whose functions are summarized in its name, Transport Erection Launcher.

The vehicle, made in West Germany by the MAN Corp., features an ability to "squat" in order to be loaded into an airplane. When a field position is established, the missile is merely elevated and fired.

In field maneuvers before a NATO evaluation group in September, the new Pershings performed much better than expected, passing tests with "flying colors," Middleton said.

In the only accident so far, one of the trucks, with an unarmed Pershing aboard, tipped over into a ditch after the drivers had gotten out to inspect a muddy road. Even though the missile carried no warheads, the accident sparked a furor when protest groups spread rumors that the area had become contaminated by radiation.

Each battery is divided into three platoons of three missiles. The platoons, led by captains, comprise 44 persons, including drivers, crewmen, radio communicators, mechanics, wiring specialists and security guards. The three missiles in each platoon require 24 pieces of supporting equipment.

The basic mission of the Pershing platoons, according to officers, follows this scenario: move the missiles aboard the trucks, preferably at night or a time when detection is minimal, into hidden positions, not far from a road for quick maneuverability to new positions.

An advance guard is sent ahead to secure a field position, then the missiles are emplaced in a firing mode as quickly as possible.

"It's one of the most rewarding, high-performance jobs I've done in the Army," said Capt. Randy J. Garibay, one of the first Pershing II platoon leaders. "You establish this close-knit teamwork, with different skills meshing like clockwork."

In spite of their enthusiasm for the missile's capabilities, officers said they would be quite willing to sacrifice their new arsenal if an arms control deal can be struck with the Soviet Union that would reduce or abolish medium-range missiles in Europe.

"I would be more than happy to take the Pershing II home, even if it put me out of a job," Middleton said. "But not through unilateral disarmament."