Lebanon's militant Christian forces challenge the old-guard establishment

The Christian community in Lebanon appears to be on the verge of a major shake-up. The Lebanese Forces, the militia that spun off the Phalange Party and other Christian political groups in the 1970s, has indicated it will in effect try to take over those traditional bodies.

''We will find a way to use this new blood to purge the parties,'' explained Ared Mahdi, cofounder of the militia and a member of the Phalange Politburo.

''The Lebanese Forces is made up of aggressive, intelligent, and loyal people. These forces are the best and only legitimate route for change in our Christian community,'' he said.

Mr. Mahdi conceded that this would amount to a takeover from the influential warlords who have dominated politics during Lebanon's 40 years of independence. The militant second generation of Christian leaders now bidding for power grew up not in the days of sectarian coexistence but in the subsequent years of civil war.

The significance is not the change in names at the top, but the effect on Christian positions in the coming negotiations on reforms that would even the balance of power between majority Muslims and minority Christians.

The negotiations are a crucial effort to eliminate the root cause of strife.

The younger leaders are much more hard-line about preserving their identity and supremacy in the last Christian stronghold in the Middle East.

The intentions of the more outspoken younger Christian leaders typify the latest trend in Lebanon: The war generation, those Christian and Muslim youths who have carried the guns during a decade of conflict, are challenging the recognized leaders.

Increasingly, the spokesmen of the second generation are emerging as the real behind-the-scenes decisionmakers - in part because their weapons have turned them into the power on the ground, in part because they are now the majority.

The trend has been particularly notable within the Shiite Muslim Amal movement, where the militant young fighters are increasingly challenging the leadership of moderate Nabih Berri.

For the Maronite-dominated Phalange Party, the turning point was the passing last month of Pierre Gemayel, the Christian patriarch and party founder. During his career he had veto power over the increasingly independent militia.

Last Thursday the Phalange elected Elie Karameh as their new chief. But as the prestigious Middle East Reporter commented: ''Dr. Karameh cannot be but an interim leader.''

The timing appears to be ripe for a militia move, not for the first time against other Christians.

Also in the name of consolidating Lebanon's estimated 500,000 Maronites, the forces launched a war in 1980 with the Tiger militia of former President Camille Chamoun, leading the Tigers either to disperse or to integrate with the Lebanese Forces.

Mahdi, who also once headed the Lebanese Forces information office in Washington, indicated the purge would be through political channels this time, rather than use of arms.

''We need a lot of changes in the parties,'' he said. ''After Pierre Gemayel's death, there is no single person able to coordinate, no one whose judgment is accepted by all. This is the role the Lebanese Forces, as an institution, must play.

''The members of the Lebanese Forces will now go back to the parties they belong to and make changes,'' he explained. ''This will involve reformulating policy - toward Syria, Israel, the US, and then internally.''

Although Mahdi claimed the Lebanese Forces still favored coexistence with the 17 recognized religious communities in Lebanon, other militia sources contend that reconciliation must be on Christian terms - since the dominant power is now in their hands and therefore theirs to give or keep.

Due to Christian opposition to Syria, for fear of being absorbed by a Muslim state, political observers expressed some surprise when the Lebanese Forces agreed to go along with the peace plan orchestrated by Damascus this summer. But that was also when Pierre Gemayel, father of the Lebanese President, was still a major power.

There is already strong suggestion that the Lebanese Forces commander, Fady Frem, may soon be replaced by a more militant figure.

Among those named by Mahdi as potential militia chiefs were Eli Houbeika, a man listed in the Israeli report for involvement in the 1982 Palestinian massacre; Samir Geagea, one of the most hard-line Christian fighters; and Fuad Abu Nader.

Western diplomats say the possibility of takeovers of the traditional parties , either Christian or Muslim, by the angrier and more daring youths will make the already difficult reconciliation process almost impossible.

The trend led to a commentary Sunday in Lebanon's Monday Morning magazine: ''This generation, product of events that shook Lebanon to its foundations ... does not belong to us. It is not Lebanese.

''This is the generation that will have to deal with the coming conflicts and responsibilities.... (But) today father and teacher are confronted with a rebellious, disobedient, and wayward generation. There is little, if any, room for understanding.''