Beirut — Shortly after midnight Monday, Lebanese Army trucks and armored personnel carriers rumbled through Beirut's port at the beginning of an operation to take over the famous ''fifth basin.''
By dawn, the pier was eerily quiet and empty, its gate locked and guarded by Lebanese troops - a stark contrast to the bustle and noise of stevedores and ships at the other four docks.
The takeover was the latest in a series of moves to end the eight-year era of chaos in Lebanon and to reestablish government authority over the private militias that had, in effect, ruled Lebanon.
The fifth basin was taken over because it had been controlled since the 1976 civil war by right-wing Christian gunmen of the private Phalange militia. The militia reaped vast profits from customs revenues actually due to the government.
Although there has been much talk about the restoration of sovereignty over all of Lebanon to the government of President Amin Gemayel, Western diplomats and Lebanese had begun to express deep concern about the lack of concrete action since his inauguration last September.
In mid-February, the government launched the ''Greater Beirut plan'' designed to put the Army in control of east Beirut in the same way it had controlled Muslim-dominated West Beirut since the PLO departure last August. This effectively unified the capital for the first time since 1975. The Army has had minimal control of the Christian-dominated east over the past six months in the form of patrols to check for visible signs of Christian militia operations. Now there are checkpoints ringing the capital, and it is illegal for militiamen to carry guns or wear uniforms. Other moves in the campaign include:
* Closing down the offices of foreign political parties, such as the Kurdish ''Par Ti,'' which proliferated in Beirut. Most Arab countries had both dissident and support groups in Beirut, often fighting each other and adding to the internal tension.
* Banning displays, slogans, or flags likely ''to provoke opposition between one group of citizens and another and (that) may upset public order in any way.'' There is also a prohibition of speeches, songs, and marches by groups that might ''incite rioting.''
During eight years of fighting, shop windows, fences, and apartment-building walls were splashed with the posters, flags, and graffiti of an estimated four dozen rival factions. The groups became competitive about the quality and quantity of their symbols.
Now only advertisements and Army recruitment posters decorate drab exteriors.
* Making rulings that forbid publication of ''false reports likely to incite public opinion,'' and articles or illustrations considered ''disturbing to security.''
Military Public Prosecutor Asaad Germanous was quoted as saying the measures did not cover the press. However, he has subsequently started proceedings against An Nida, a leftist newspaper, for ''contempt of the Army,'' after it published a story critical of Lebanese troops.
The port operation was particularly important, since it represented consolidation over a strategic area with both political and economic advantages.
Before the civil war, fees related to shipping and importing accounted for almost half of the national income. After 1976, they amounted to only 15 percent. Commercial attaches estimate the total loss over the years at a staggering $1.25 billion because of the fifth basin and 17 other smaller illegal ports along the Mediterranean coast.
However, the retaking of the port also brought out one major weakness in the plan. As with many events in Lebanon, the takeover arrangement was reportedly not as straightforward or easy as it might seem.
Lebanese sources and Western diplomats suggest that the Phalange insisted on a quid pro quo from the government in exchange for giving up the dock - the single largest source of its income. The exchange involved a guarantee that the Phalange would receive funds to replace the lost revenue, according to the sources, which may in turn be paid from fees the government collects at the port.
One Lebanese source suggested that the price might be worth it in the long run, since the psychological gain of appearing to restore authority over all of the capital marked the government's first major success.