LONDON, JAN. 30 -- Iraqi President Saddam Hussein is under the protection of a special security unit of about 15,000 men designed to guard him not only from outside attack but from assassination by his senior military commanders, according to Iraqi exiles and informed British sources.

The unit, which the sources say was beefed up after the invasion of Kuwait, may have helped thwart a coup attempt by air force officers that Soviet intelligence sources are said to believe took place last week. The Soviets reportedly said the sudden flight of Iraqi military aircraft to neighboring Iran was related to the coup attempt and to Saddam's alleged execution of senior air force and air defense commanders.

Intelligence data from inside the Iraqi hierarchy is sketchy at best, and officials here say they cannot confirm the Soviet intelligence assessment or the reported executions. But the existence of the special unit underscores the difficulties allied forces face in seeking to achieve one unacknowledged but central aim of the Persian Gulf War -- the removal of Saddam as leader of Iraq.

According to analysts, Iraqi opposition figures and officials here, the removal of such a well-guarded, experienced and ruthless survivor is technically difficult. In addition, the allies' military campaign may actually be further entrenching Saddam's support inside Iraq.

Some of the regime's most dedicated opponents already say they feel compelled to limit their criticism because of the damage the bombings are inflicting on Iraqi civilians. "We want Saddam Hussein to be toppled, but our people are suffering," said Sahib Hakim of the Organization of Human Rights in Iraq. "I fear the bombing is pushing more people to support Saddam."

Saddam is hard to remove in part because he and his followers came to power through a military coup and are determined to keep others from following the same blueprint.

To prevent that from happening, Saddam has repeatedly purged the armed forces of senior commanders and set up a layer of security between himself and even his most trusted officers. The special guard unit consists of members of the Amn al-Khass, the Soviet-trained internal security organization, and the Estikhbarat military intelligence bureau, Iraqi sources say. Its leaders are members of Saddam's own extended Tikriti clan. Some 600 to 700 guards are said to accompany him at all times.

"It's like plotting against {Adolf} Hitler," said an Iraqi opposition member. "He may lose all popular support, but someone has to kill him to defeat him and that's hard to do."

Saddam has been in trouble before. In 1982, an Iranian counteroffensive recaptured most of the territory Iraqi forces had seized at the start of the Iran-Iraq war and began to encroach into Iraq.

The Iranians called for the ouster of Saddam and his trial for war crimes. There were Shiite riots in Iraqi cities and two assassination attempts. Even some of Saddam's closest political associates lobbied for his departure so that a cease-fire could be negotiated.

But Saddam did not fall. The regime intensified its repression of Shiite dissidents, while the Baath Party hierarchy, faced with the Iranian demands, rallied around its leader. Saddam reorganized the country's Revolutionary Command Council, restricting it to his closest allies, and arrested and later executed some who had opposed him.

One of the hardest elements for outsiders to understand is the relationship between Saddam and the people he rules, analysts say. On one level, the regime is said to function on pure terror: ordinary Iraqis live under fear of arrest and execution, just as ordinary soldiers "Someone has to kill him to defeat him and that's hard."

-- an Iraqi opposition member

fear arrest by the Republican Guard. Reprisals are taken not just against purported dissidents but against entire families, by this account.

At the same time, however, the regime has managed to win and hold the support of sizable segments of Iraqi society outside the immediate ruling circle. Using the vast oil revenues available to Iraq after 1973, the government financed major improvements in health and education and assisted a generation of rural dwellers who migrated to Iraq's cities.

"We have to acknowledge that just as Saddam built the system, in some ways the system built Saddam," said Samir Khalil, author of "Republic of Fear," a detailed account of the regime. "The number of people involved in the repressive apparatus was huge, and many more benefited from the regime."

The Iran-Iraq war deeply eroded Iraqi prosperity and Saddam's decision to build up his military rather than rebuild the country after the war's end was highly unpopular. One reason he invaded Kuwait was to shore up popular support by championing a cause -- Iraq's historic claim to Kuwait -- that many believed was legitimate, said Peter Sluglett, an authority on Iraq at Durham University.

By now, however, analysts say, much of that support has waned. Many Iraqis are said to blame Saddam for the bombs falling on their cities and few seem to share the romanticized view of Saddam as Middle East hero -- as held by many foreign Arabs who have never lived under his rule. But some Iraqis fear the country will dissolve into Lebanese-style civil war after he goes.

"Iraq is a mosaic state -- there are Sunnis, Shiites, Kurds and all sorts of divisions," said an exiled Iraqi political scientist. "A lot of Iraqis who don't like Saddam nonetheless believe he is the only thing holding the society together. They have a fear of the unknown."

This academic said the way to weaken Saddam is to defeat Iraqi forces in Kuwait and to destroy the apparatus of the regime. "It will take time, but people will begin to realize that if Saddam remains in power, no outside country will help Iraq rebuild itself," he said. "In the end, he will lose."