Beirut — In his west Beirut apartment, a Lebanese Army colonel sat frustrated and bored, occasionally glancing nervously out a window at the rippling Mediterranean.
He has been barely active for two months, ever since the Army split along religious lines because of a government order for the Christian-led Army to attack Muslim-dominated west Beirut.
''There is still hope for this country,'' he said somewhat forlornly. ''One hope. It is the Army. We may have split into two armies, but we still have not fought each other, and we can still be put back together again.
''It is different from (the civil war of) 1975-76 when so many left to join the militias. This time we stayed in ranks and did not turn over equipment. I want to be one army again, and so does every soldier I know. But there is not much time left.''
The status of the Lebanese Army may be the one thing both Christians and Muslims in this divided country agree on. All sides claim the reunification of the armed forces would mark the real success of the troubled reconciliation effort.
There are, in effect, two armies in Lebanon: one loyal to the state and, like the government, Christian-dominated; and a second, now cooperating with Druze and Muslim militias that represent the majority of the population. One of the bizarre twists to the division between east and west Beirut is that both sides rely on the Army for security and basic functions of law and order.
Another is that the government still pays officers and troops who, in any other army in the world, would be considered to have gone AWOL. And there continue to be contacts between the two sides, according to Army sources and United States military advisers who have been training the resurrected Army for the past 16 months.
That the ''second'' army has gained quasi-legitimate status was reflected by the evaluation of the US marines who handed over their positions at Beirut airport to the Muslim 3rd and 6th Army brigades.
''One good thing about the rebellion was that it was not aimed at the Army per se, but against the government and its use of the Army,'' a key Western military source said. ''And it could go back together rather quickly in the right political environment.''
Indeed, the rebuilding of the Lebanese Army, begun in late 1982 by a team of US Special Forces and Rangers, may be the only comparative success story of the US presence here. Lebanese officials in both armies concede that the ''Lebanese Army modernization program'' did manage to hammer a new sense of discipline and loyalty into the armed forces, in a country where religious allegiance has been stronger than national identity.
Since the breakdown on Feb. 6 when Muslim militias took over west Beirut, Washington officials have blamed the US trainers for overoptimistic evaluations of the Army's potential. Yet diplomats and sources close to the trainers claim that repeated advisories warned of the dangers of injecting politics into a still fragile situation that might force conscripts and officers to take a stand.
Ten days before the turning point, a US military analyst correctly predicted that the Army could not be used on a major offensive until a national-unity government was installed. Such a government would be needed, he said, to prevent the two major Muslim sects and the Druzes from charging that the Army worked only in the interest of minority Christians who still had a tight grip on the government.
''Rebuilding the Army has worked. But it really cannot be effectively used, except defensively, until there are some political changes in Lebanon,'' he said at the time.
Slightly more than half the combat-ready troops defected in the aftermath of Feb. 6, taking tanks, armored personnel carriers, and guns with them, according to Western estimates.
President Amin Gemayel's government had not heeded a warning some five months earlier when an estimated 1,100 Druze officers and troops walked out as the Army took on the Druze militia in the Shouf mountains. Two Lebanese intelliaence officers warned at the time of long-term dangers of further defections unless the government stopped ordering its new ''national'' Army to attack its own people.
Shiite Muslims, the largest religious group in the Army, laid down their arms or returned to their barracks rather than fight their own people in February. The only significant Muslim presence in the Army now is Sunni.
Officials from the 3rd and 6th brigades blame the Christian-dominated government for inaction on the key issue of adjusting political power-sharing. They want the composition of the government to reflect the redistribution of numbers and power among the 17 recognized sects in the Army.
Just before the breakdown, the Army - up from 12,000 soldiers in 1982 to 37, 000 - was 57 percent Muslim and 43 percent Christian, although Christians still had a slight edge at the officer level, according to the US trainers.
A Christian officer on the ''green line'' that divides Beirut put it differently: ''The Lebanese Army is an excellent school for patriots, but inherently weak as a fighting force because of the absence of an esprit de corps in the country to back it up. Political leaders are responsible for this sad state of affairs.''
The US training program is the only major American presence in Lebanon, after the Marine pullout and the end of the US peace initiative. But the corps of trainers, once numbering 200 people, is down to 50 because the Army has ''temporarily suspended'' recruiting and drafting men.
There is also some danger that the US program could end at midyear because of Lebanon's financial woes. In the past 16 months the government has spent $1 billion to rebuild and reequip the Army. Lebanese sources say only US loans would allow the program to continue, since the government also has to consider infrastructure after nine years of war.
A key Western military expert with long experience in Lebanon says there are two alternatives for the Army - both depending on political developments:
''If the nation becomes cantonized, so does the Army, with the regular Army doing housekeeping duties and the militias institutionalized as national guard units with their districts. But if the nation comes back together, the Army would once again become the major force here.''
The Lebanese Army colonel was not optimistic. ''The longer this government waits for its supposed 'new Lebanon,' the less the chances for the Army. One more big round of fighting, like in February or September, and the division could become permanent.''