Managua, Nicaragua — The downing of a Nicaraguan contra rebel resupply plane Saturday night is only the latest reminder that despite all the talk of peace, there is a very hot war under way in Nicaragua. There have been several important changes in this war over the past year, military and diplomatic observers say.
``The war is stalemated now, this is certain, and it will remain that way regardless of the amount of aid the contras receive from the United States government,'' one Western diplomat here said. ``And even though that equilibrium is unlikely to be broken, the rebels' success has been to have gained that equilibrium.
``What has changed is that the contras have taken the tactical initiative, [although] at no moment will they be able to defeat EPS [the Sandinista Army].''
The ``tactical initiative,'' diplomatic and military observers say, is due primarily to the contras' use of Redeye antiaircraft missiles and their deployment of more sophisticated communications equipment.
The use of the highly accurate Redeye has forced the Sandinistas to use ground transport for moving troops, cutting down their reaction time, these observers said. It has also taken away the great advantage they had in deploying sophisticated helicopter gunships as a first response to an attack.
``The rebels have neutralized the Sandinista helicopters with the Redeye,'' said the Western diplomat. The Sandinistas ``have tanks and artillery, but they cannot use them effectively against the rebels. This is now an infantry war between men with 50-pound packs on their backs.''
The rebels received the Redeye missiles last year under the $100 million aid package passed by the US Congress in 1986. The Redeyes have shot down between 10 and 26 Sandinista helicopters in the past year, depending on which side one speaks to.
The use of the antiaircraft missiles was largely responsible for the contras' ability to mount their largest attack ever in late December, in northeastern Nicaragua. Hundreds of rebels overran several Army positions and reportedly made off with a sizable cache of arms and food, one Latin American diplomat said.
``As long as the resistance can keep being supplied by air, they could maintain the tactical initiative,'' the Western diplomat said. ``Without [US] aid, however, they would not last out the end of the year.''
No Sandinista military officials would be interviewed for this article, despite numerous attempts over seven days.
But in the past the Sandinistas have often said their war with the US-backed rebels is as political as it is military: a battle for the loyalties of the Nicaraguan people, as much as one between soldiers.
``There is no such thing as a `military victory,''' said the Western diplomat. ``All military victories are political in wars like these.''
``The rebels have support in the interior, in the mountains,'' the Latin diplomat said, ``but they have not been able to launch a single attack on the Pacific plain,'' where the majority of the population live. ``This is a great problem for them.
``One reason,'' he said, ``is that the contras lack political support in the more populous regions.''
Bosco Matamoras, a contra spokesman, said the rebels have support in the Pacific plain and the cities, ``but we have decided as a strategy not to bring the war there. We have the tactical initiative now and will strike where we want and when. And where we have the advantage,'' Mr. Matamoras said.
That there is discontent among the Nicaraguan people - particularly in the cities, and especially Managua - over the collapse of the economy is agreed to by most observers here.
But what is uncertain is whether such discontent translates into direct support for the contras, the kind that could be used to open a military front in the cities of the Pacific plain.
``The war is costing the Sandinistas support. The tactic of the rebels is to attack the economy - [farm] cooperatives, productive sites, roads, and the Sandinista political infrastructure. This will continue and is more effective than military victories,'' said the Western diplomatic source.
Perhaps the most important question for those opposed to the Nicaraguan government is whether the civilian opposition can capitalize on that discontent to challenge the government politically while the contras continue the war in the isolated mountains.
The Sandinistas say they still maintain the loyalty of the majority of the Nicaraguan people, which a top comandante recently claimed was as high as 70 percent. The next important measure of that support, or lack thereof, will be the municipal elections expected to be held sometime this year.
And the outcome of those elections could be a more significant victory for the winners than any single battle fought by the opposing armies.
But until then, the shooting war continues in the countryside. And as one Western official said, the contras are certain to launch another spectacular attack before the US Congress votes next week on the Reagan administration's aid package.