The Salvadorean Army ushers in the new year with an old problem: poor morale. Two serious defeats in the last two weeks may forbode an accelerated disintegration of the fighting capacity of the armed forces, many observers here speculate.
The defeats come at a time the Reagan administration reportedly is preparing a request for $100 million in new military aid for El Salvador to increase the size of the nation's armed forces.
This past autumn, troops suffered a series of losses at the hands of the five-group guerrilla coalition known as the Faribundo Marti National Liberation Front (FMLN).
A four-month-old guerrilla offensive reveals not only an increase in rebel strength, but also the failure of Salvadorean government troops to:
* Initiate attacks against rebel contingents.
* Hold government positions.
* Ascertain where and how guerrillas will strike.
The guerrillas' recent capture of the Fourth Infantry Brigade headquarters in El Paraiso and their destruction of the Cuscatlan bridge, this country's largest , illustrate what have become perennial problems for the military.
Critics of the military, such as former commander in chief Gen. Jaime Abdul Gutierrez, charge that the failures are due to a lack of Army motivation rather than a shortage of manpower or equipment.
The overrunning of the garrison - once proclaimed impregnable by the Salvadorean high command - by 300-500 guerrillas Dec. 30 has sent a tremor through the military. It marks the first time rebels have taken control of a major Army installation. Despite US interest in enlarging the size of Salvadorean armed forces, the military here does not appear to be talking about such a plan.
''We are losing the war,'' says a high-ranking Salvadorean military official, ''and the only way to salvage the situation is to give the troops something to fight for. Until that time, we cannot be saved, no matter how much military equipment arrives from the United States.''
The Salvadorean Defense Ministry, which has yet to acknowledge the Dec. 30 capture of the garrison, conceded that ''more than 100 soldiers'' died in the guerrilla assault 37 miles north of the capital. An estimated 250 soldiers were defending the fort. It was the largest single Army casualty report in the four-year conflict.
Military observers here attribute the 12-hour occupation and destruction of the base to less-than-adequate monitoring around its perimeter and an inability by the Army to monitor guerrilla movements. They also charge that many of the troops stationed at the base were on maneuvers, although guerrilla and other sources claim many were on holiday leave. After 12 hours, guerrilla forces withdrew from the garrison.
The base was designed by US counterinsurgency experts to prevent just such a surprise attack. It was spread out over several hilltops ringed by a defense zone.
''The problem,'' admits a military observer, ''is not our strategy or tactics but our execution.''
Two days after the loss of the base, rebels destroyed the quarter-mile-long Cuscatlan bridge. Its destruction has severely restricted traffic to the eastern third of the country. It also brings guerrilla forces a step closer to declaration of a liberated zone in eastern El Salvador.
Rebels met token resistance from 200 National Guard ''cadets'' guarding the bridge. Some residents say many of them were preoccupied with a New Year's Eve party.
The guerrillas apparently held the bridge for 2 1/2 hours. The bridge was the crucial link from the capital to the eastern provinces, where the main cotton and coffee farms are attempting to bring in the harvest.
Nearby Army reinforcements failed to mobilize to save the structure, although military observers say they had more than enough time to make it to the bridge. The Army high command has attempted to cover up the extent of its losses and poor military performance.
The bodies of at least 100 unidentified soldiers killed in the attack on the garrison were bulldozed into a mass grave in a cemetary in Chalatenango. Two days after the burial the Army was sighted in two western provinces pressing teen-agers into the military at gunpoint.