An old man in traditional checkered headdress gestured at the devastation left in this central Syrian city by three weeks of relentless pounding by government artillery and tank cannons.

"What happened here has happened nowhere else in the world, not in the foreign world, not in the Arab world," said the old man, who lost a brother and two nephews in the February siege. He shook his head, then looked toward the sky. "Allah was watching. We are counting on Allah."

The scale of the retribution meted out by President Hafez Assad's government against Moslem Brotherhood rebels has become clear only recently as the city, for weeks declared closed to outsiders, has been reopened. More than two months after the siege, the scene is still one of widespread destruction.

Entire neighborhoods have been reduced to rubble. Bulldozers are still flattening crumbled buildings, leaving empty lots the size of four football fields where prosperous market stalls and centuries-old Islamic landmarks once graced the banks of the Orontes River. A government committee recently reported that it will cost more than $500 million to repair the damage.

The cost in lives was also high. Diplomatic sources estimate that more than 5,000 civilians were killed. There are approximately 20,000 orphans.

The government's military operation apparently was designed to end permanently Hamah's role as a center of Moslem extremism and antigovernment agitation. This was done by blasting the spirit of rebellion out of Hamah, administering to its 300,000 residents a lesson no one here ever will forget.

"They the military didn't endear themselves to anybody, but they certainly showed what they were willing to do to survive," said an experienced European diplomat. "The regime bared its teeth."

Walking down muddy lanes bordered by destruction on both sides and traveled only by a few bent old men, it seems clear that the Islamic rebels were well-armed and resisted violently to the death. It also appears that the Damascus government, which consistently reported that its forces were engaged in a small-scale police action, misrepresented both the size and the ferocity of its attack.

The attack's aftermath was "traumatic," another Western diplomat said, leaving the brotherhood in shambles and a broad swath of Syrians unsympathetic to Assad's rule in a state of shock and resignation.

"They are sure the brotherhood will try to rebuild," he added. "But it will take six months or even up to a year before they can mount operations against the government."

The Hamah uprising was the most extensive challenge to Assad's government since he assumed power in a bloodless military coup 12 years ago. It climaxed a sedition campaign that began in the spring of 1979 but now apparently has been stopped.

The destruction here showed that, despite many other strains--including an Air Force coup plot uncovered in January while still in the planning stages--the Damascus government can still count on its 220,000-member armed forces for support.

Although individual defections were reported among troops ordered to fire on Hamah civilians, diplomats in Damascus report, there were no large-scale desertions during the siege. Forces deployed against the city included regular soldiers, militia from the ruling Arab Baath Socialist Party and elite troops from the Defense Brigades headed by the president's brother, Rifaat Assad.

Youths in civilian clothes carrying AK47 assault rifles or pistols in their belts still oversee checkpoints at the main entrance to the city. But the streets today are free of troops as vegetable sellers set up makeshift stands on the edge of what was the ancient Hadhir market area--now a vast, empty lot.

Similar checkpoints have been set up on all roads leading into Damascus, the capital 120 miles south of here. Civilian youths with hand grenades and ammunition clips on their belts lounge by panel trucks at key Damascus intersections as soon as the sun goes down.

Trucks crossing Syria are required to travel in escorted convoys to make sure they leave the country. A panel truck blew up in the crowded Azbakiyeh Quarter last November, killing about 200 persons and a six-wheeler was discovered parked in the central Omayyad Square in January with enough explosives to level an entire neighborhood.

Assad's government blames the sedition on Moslem Brotherhood extremists aided mostly by President Saddam Hussein's rival government in Baghdad. In an effort to cut off supplies to any more would-be rebels, Syria last month closed its borders with Iraq, halting a busy transit trade through Syrian ports. There are reports that the government is considering closing borders with Jordan, also accused of harboring Moslem Brotherhood rebels.

With the tough reaction against Hamah and stepped-up security precautions, diplomats in the capital say Assad has consolidated his grip on power and, in the words of one analyst, "bought himself some breathing time."

To the conservative Sunni Moslem population here, Assad's Baathist rule and its secular ideology have long been a source of resentment. Assad has accepted Islam as a source of jurisprudence in Syrian law, but refuses to make it the state religion.

In addition, Assad has grouped around him in key Army and goverment posts members of his Alawite sect, an offshoot of Shiite Islam. Syria's Alawites, who make up 12 percent of Syria's 10 million inhabitants, traditionally played a secondary role in the mostly Sunni Syrian society until Assad's rise to power.

These political considerations seem distant from the flat dirt space where the historic Keylani family home once stood proudly beside Hamah's famous wooden water wheels, or from the shell holes in the 18th century palace museum across the Orontes.

But, diplomats say, they have been important for years to the people of Hamah and have been etched more deeply into their minds by February's shelling and mass destruction.

"No one will forget," the old man said, walking past a blasted-out home.