Jerusalem — As a purely military exercise, Israel's invasion of Lebanon was a landmark performance.
After the anxieties aroused by the Arab-Israeli war of 1973, with its blunders and shortcomings, the operation in Lebanon revealed a new Israeli Army honed to an unprecedented level of cool efficiency.
The dimensions of the Israeli war machine were evident to observers watching the invasion force enter south Lebanon in the opening days of the war - even before the bulk of the fighting began. The convoys rolled across the border endlessly, day and night. They displayed not only an immense concentration of power - more than Israel had ever brought to bear on such a narrow front - but also surprisingly modern equipment as well as an orderliness and self-discipline unlike any the Israeli Army had ever previously known.
In the past, the Israeli ground forces have been distinguished by boldness and improvisation. But their equipment has often been hand-me-downs. Bread vans and other mobilized civilian trucks in the past made up a good part of their supply fleet in time of war. Dress and deportment sometimes suggested a partisan band rather than a modern army.
After the 1973 war, a government-appointed commission issued a damning report. It found the Army ill-equipped, ill-maintained, and ill-disciplined.
The informal ways of a people's army had long been one of the Israeli Army's strengths in promoting morale. But these ways - offi-cers and men on a first-name basis, no saluting, lax dress - also led to laxness in more critical areas like vehicle maintenance. Such laxness resulted in costly breakdowns when fighting broke out.
In the years since the war, the Army has invested great efforts in restructuring itself along more professional lines without slipping into Prussian-style discipline. The current conflict in Lebanon revealed the stunning manner in which it had succeeded.
This success was apparent in Israel's ability to mobilize large reserve forces at very short notice in secrecy and move them up to the front battle-ready. Reservists arriving at their unit's emergency mobilization depot found perfectly conditioned tanks and other war equipment waiting for them. Protective wrapping was quickly stripped off vehicles, uniforms donned, engines ignited, and the units began streaming north.
Vehicle breakdowns were minimal. This attested to a high level of maintenance and an elaborate network of field maintenance units accompanying the troops. They swiftly effected any repairs necessary, replacing tank engines at the side of the road as if they were flat tires.
Although some units in the invasion were still equipped with World War II-vintage half tracks and were accompanied by civilian supply vehicles, the bulk of the force displayed a new modernity for the Israeli Army.
A military attache from Western Europe in civilian dress watching the Army cross the border at Metulla said he was most impressed at the demeanor of the troops. ''They're professionals,'' he said, aware that the bulk of the force were young draftees and reservists.
The fighting itself was far more gruelling than the initial laconic reports of the Israeli Army spokesman indicated. Rugged terrain on the eastern sector provided ideal defense positions for the Syrian Army, which put up a fierce fight. On the western sector, Palestinians were credited by Israeli troops with having fought bravely as they attempted to mount ambushes in guerrilla fashion in orange and olive groves and in built-up areas.
The Israeli Army was able to test in battle much new equipment, including the Israeli-made Merkava tank, which reportedly emerged well from its baptism of fire. The tank is said to have beaten the top tank in the Soviet arsenal, the T- 72.
The Israelis also apparently coped with the problem of antitank missiles from enemy infantry - a problem that had plagued them in the 1973 war. The Israelis solved this problem in Lebanon by sending out their own infantry to clear a path. But the most sensational success was the destruction by the Israeli Air Force of the Soviet-made SAM antiaircraft batteries in the Bekaa Valley and of almost one-third of the Syrian Air Force.