Rear Adm. Robert P. McKenzie sees himself as a man on a mission, not a victim of one of President Carter's political ploys as some of his peers suggest.

McKenzie commands the Caribbean Contingency Joint Task Force which Carter established here a year ago this month in response to the Soviet refusal to remove that "unacceptable" combat brigade from Cuba 90 miles away.

"This will substantially improve our capability to monitor and respond rapidly to any attempt military encroachment in the region," said Carter on Oct. 1, 1979, in announcing the new command.

But the CCJTF -- Caribbean Contingency Joint Task Force -- consists of only 70 officers and enlisted people, representing all four services, and thus is a joint planning staff, not an outfit to take on the Soviet brigade.

"As useless as a tit on a boar hog," scoffed one senior military officer, insisting that everything done by the new command in Key West could be done just as easily at Atlantic Command headquarters in Norfolk, which supervises the operation here.

Besides, the Pentagon's old boy network is passing the word to commands that the Carter administration already has decided to close down the CCJTF headquarters here after next month's presidential election, no matter who wins.

Admiral McKenzie said in an interview that he has heard those rumors, too and conceded that perhaps the CCJTF was indeed created initially for political reasons.

"It might have been politics. I don't know what the reasons were," said MdKenzie in his office on the top floor of the refurbished submarine school at the sprawling Key West naval base.

But now that the CCJTF has been in business a year, McKenzie contended, it has proved its worth, no matter what the critics say.

"The creation of this staff has filled a very valid military requirement," McKenzie said. "The staff has been able to focus on an area of the world we have neglected for 15 years."

He compares his mission to that of Commodore David Porter, who established the first U.S. naval base here in 1923. Porter commanded 17 ships which sailed forth from Key West to cleanse the Caribbean of pirates who were marauding merchant vessels.

Admiral McKenzie sees the United States today confronted with another pirate -- Fidel Castro of Cuba. Accusing Castro of picking on weaker nations in the Caribbean, he expressed the problem this way:

"During the last 15 years, we have left a rotten apple sitting in the barrel and it has contaminated a significant portion of that barrel.

"I hope to God they don't disestablish this headquarters," the admiral went on, because it enables the United States to keep an eye on that "rotten apple." Declaring that he has heard "beyond rumors, nothing" about Carter administration plans to close his command headquarters here, McKenzie revealed that he has asked the Joint Chiefs of Staff to increase his staff by 30 people. This would bring it to a force of 100, about half the size of an Army infantry company.

"No one who has ever come down here has left doubting the validity of the existence of this staff," McKenzie said.

Visitors are given an elaborate briefing on what the CCJTF has done in its first year. An officer standing at a microphone in front of the room delivers a lecture while slides are shown on three different screens.

The briefing states at one point that "the United States must respond to this threat of Castro influencing his Caribbean neighbors. Recent events in Nicaragua, Grenada, Jamaica, and El Salvador reflect the success of these subversive efforts."

At another point the briefing warns that Soviet ships operating out of Cuban ports could strangle western shipping which must move through one of the three straits off Cuba.

The CCJTF presentation reminds the listener that the staff here planned several naval exercises in its first year, including two into Guatanamo Bay on Castro's Cuba. But as it turned out, the CCJTF's shining moment had nothing to do with the Soviet combat brigade that gave birth to the command at Key West.

Instead, the CCJTF got the nation's attention as it planned the boatlift of 115,000 Cubans from the island to the naval base here and on the camps or homes in the United States. President Carter called off that boatlift as the number of refugees threatened to overwhelm the U.S. ability to absorb them.

Once Carter had halted the boatlift, the Coast Guard confiscated any boats that tried to violate the ban and transport Cubans to the United States at prices up to $1,000 a person. Some 200 of the confiscated boats are now tied up at piers or spread around the nearby pavement like so many beached whales.

Directly across from one of the confiscated boats, named Long Life, is a plague commemorating Commodore Porter's stand against the pirates. And a sign has been hung on the pier where so many thousands of Cubans entered the United States. It bears a message that McKenzie hopes will not apply to the new stand taken here.

In Spanish, it reads: "Por Favor La Ultima Persona Que Salga De Cuba Que Apaque Las Luces."

In English: Will the last person leaving Cuba please turn out the lights.