Washington — For the first time in more than a decade, Cuba's troops and diplomats are on the defensive on several fronts. Grenada has not been the Cubans' only recent setback.
Some 600 miles to the southeast of Grenada, on the very day of the Grenada invasion, left-leaning Surinam ordered Cuba's ambassador to leave.
In recent months and years, voters on small islands to the north of Grenada - Dominica, St. Vincent, Antigua, and St. Lucia - have elected conservative governments. If Cuba was trying to ''export revolution'' to those islands, as President Reagan says, it was not doing very well.
In Angola, insurgent troops have for the first time launched sustained offensives, throwing the Cubans and their Angolan allies on the defensive.
In Ethiopia, an economic disaster of a country, the Cubans are not associated with anything approaching a success story.
Cuban President Fidel Castro obviously hopes, through diplomacy, propaganda, and other means, to exploit the opposition that has surfaced against the United States as a result of the Grenada invasion. But it is not clear to what extent he will succeed, if at all.
Diplomats from a number of key Latin American countries have told State Department officials that while they publicly oppose American intervention of any kind, they privately applaud the Grenada action. Venezuelan officials were described as ''relieved'' by the expulsion of the Cubans from Grenada.
State Department officials hope that documents captured on Grenada will help persuade other allies in Latin America and Western Europe that the invasion was justified. Among the three quarters of a ton of documents are five secret treaties concluded between Grenada and Cuba, the Soviet Union, and North Korea. These cover military aid to the island of some $38 million from the Soviets and North Koreans and deliveries of arms that State Department officials say were too extensive to be strictly for Grenada's self-defense.
According to the officials, Grenada has an Army of 1,500 men and was training a militia of 2,000 to 4,000 men. The documents indicate that the Soviets were to deliver to Grenada, among other things, 4,000 Soviet AK-47 automatic rifles, 2, 500 carbines, 7,000 mines, 15,000 grenades, 1,050 pistols, 293 snipers' rifles, 60 armored personnel carriers, and 74 rocket-propelled grenade (RPG) launchers. North Korea was to provide 1,000 rifles, 80 machine guns, and 50 RPGs.
Administration officials say the documents substantiate their charge that Grenada, an island of only 110,000 people, was receiving more military equipment than it needed for purely defensive purposes.
In a speech to the Associated Press Managing Editors conference in Louisville , Ky., last Friday, Deputy Secretary of State Kenneth W. Dam said that prior to the US-led invasion, the disintegration of political authority in Grenada under a leftist-led military council had ''created a dynamic that spread uncertainty and fear and that made further violence likely.'' The island's military leaders, Mr. Dam said, ''would have either driven the island into further chaos or turned it into an armed fortress.
''In either event, the threat to US citizens and to the peace of the eastern Caribbean would have increased,'' he added. ''Inaction would have made a hostage situation more likely and increased the costs in lives of any subsequent rescue operation.''
But there is no clear evidence in the captured documents to indicate, as President Reagan charged in a major address on Oct. 27, that ''a Cuban occupation of the island had been planned.''
What the documents do say is that Cuba, under its secret treaty obligations, would maintain 27 ''permanent'' military specialists on the island, including nine specialists in the general staff of the Grenadian armed forces. In addition , the treaty annex said, 12 to 13 specialists would visit the island for two- to four-month periods.
The documents indicate that the Cuban-supported Grenadian regime was meeting deep opposition from its own people. Captured records from September meetings of the central committee of the then-ruling New Jewel Movement say that the movement was suffering from a ''serious fall'' in numbers of active supporters. Central-committee members spoke of disintegrating control over the country. Some predicted that if matters did not improve, they could lose control completely within five to six months.
The crisis was compounded by a near disasterous economic situation, including heavy unemployment. Although Cuba, the Soviet Union, and North Korea were pouring weapons into the country, they apparently were incapable of alleviating its economic problems.
The crisis came to a head on Oct. 19 with the murder of Grenada's prime minister, Maurice Bishop. He had established close relations with Cuba and the USSR after taking power in 1979, but was apparently considered by some of his central-committee comrades to be a ''bourgeois deviationist.''
Although Cuba publicly deplored Mr. Bishop's murder, his death sent shockwaves through the Caribbean region that seemed to have worked to Cuba's disadvantage.
On the day of the Grenada invasion, the government of Surinam, a country on the north coast of South America, ex-pelled Oscar Osvaldo Cardenas, head of the Cuban mission there. Diplomats say that Surinam's leader, Desi Bouterse, had had close ties to the Cubans but nonetheless mistrusted them, especially after the killing of Bishop.
Some analysts say that Brazil played a major role in getting Mr. Bouterse to break with the Cubans. The Brazilians
are reported to have offered Bouterse arms, aid, and trade if he distanced himself from Cuba. According to one analyst, Brazil turned this offer at one point into what amounted to ''an ultimatum'': Break with the Cubans or come under the domination of Brazil.
The US-led invasion of Grenada may also have contributed to Surinam's break with Cuba, some analysts say.
The Cubans are on the defensive as well in Africa.
Reports from Angola, a large, Cuban-supported and leftist-leaning nation on the west coast of Africa, indicate that antigovernment guerrillas have taken the initiative.
Insurgent forces led by Jonas Savimbi of the National Union for the Total Independence of Angola (UNITA) have gone on the offensive in regions once considered to be firmly under government control. A few months ago, UNITA forces seized a town only 125 miles from Luanda, the Angolan capital. Travelers to Luanda report that the Cubans are not as welcome there as they once were.
The thousands of Cuban troops in Angola have, until recently at least, played a largely defensive role, protecting important towns and installations. But Mr. Savimbi's forces claim to have killed more than 100 Cubans in a single battle last August.
None of this means that the Cubans, with the largest military force in the Caribbean region except for the US, will now stop causing difficulties for US policymakers. The Cubans are deeply entrenched in Nicaragua and are much more numerous there than in Grenada.
State Department spokesman John Hughes said last week that the US takes seriously reports that some Americans working in Latin America are under death threats reported to have been made by Cuba in the wake of the Grenada invasion.
But Cuba has also made some peace overtures to the United States, which US officials say came in response to American military maneuvers in and around Central America this summer. On July 29, Fidel Castro told American reporters that Cuba would halt military aid to Nicaragua if an agreement were reached for all countries to stop sending arms and advisers to Central America. State Department officials say that they explored this offer with the Cubans but found little of substance to back it up.
Critics of US policy, such as Wayne S. Smith, former chief of the US interests section in Havana, say that the US has not done enough to try to reach an accommodation with Cuba.