A special "Pan-African Legion" formed by Libya for intervention outside its borders and including other Arabs and black Africans as well as Libyans played a significant role in Col. Muammar Quaddafi's recent victory in Chad, Western officials say.

The Chadian fighting marks the first test -- a success -- for Quaddafi's version of the Foreign Legion. Its deployment is seen as part of a concerted drive to build up Libya's regular Army and form such intervention forces by recruiting foreign Arabs, Asians and Africans through offers of high pay and, in some cases, simple dragooning.

The effort reflects Qaddafi's longstanding sense of pan-Arab and pan-Islamic revolutionary mission, which has led him to intervene in about 45 countries in the Middle East, Africa, Europe, Asia and even Latin America, according to an estimate prepared by U.S. officials.

It has resulted in private complaints from several African governments that their citizens working in Libya's oil economy were press-ganged like 19th century sailors -- that they were picked up in the street to awake the next day in the Libyan Army.

Senegal has protested openly that a group of Seneglese, lured to Libya with offers of jobs in a desert work camp, found when they got there that it was actually a military training camp for Senegalese Islamic rebels.

Qaddafi, whose oil has given Libya nearly boundles wealth, has voiced determination to increase the size of his armed forces to half a million to go along with the large arsenal of Soviet- and French-built weapons he has accumulated since coming to power in 1969. But his population is small -- fewer than 3 million -- and generally too unsophisticated to use and maintain modern weaponry. As a result, Soviet and East European advisers number about 3,000 and the 350,000-man regular Libyan Army ranks include Pakistanis, Palestinians and other Arab nationals.

To increase the foreign contingent and build its intervention forces, the Libyan government actively recruits among the black Africans, Pakistanis, Sudanese, Palestinians, Egyptians and Tunisians who leave the poverty of their own villages to work in Libya. Sometimes recruiting extends to Libyan prisons, where Libyan and foreign criminals win freedom from their cells for joining what Qaddafi's Army calls "suicide squads" specially trained for commando-type action.

Some of these squads participated in Libya's disastrous attempt in April 1979 to aid the then-falling Ugandan dictator, Idi Amin. In the ironic assessment of one informed official, "They generally lived up to their name."

Recently Qaddafi's aides have begun placing recruiting advertisements in newspapers in Beirut and across the Persian Gulf -- and even in Britain -- promising any Arab who volunteers for service in the Libyan Army good pay and a chance to participate in the Islamic resurgence that Qaddafi increasingly appears resolved to foster among his African neighbors as well as in the Middle East.

Although Qaddafi's money is accepted by a number of Arab governments and several factions of the Palestine Liberation Organization, his often impetuous zeal is something of an embarrassment in the Arab world, and a number of leaders there keep him at arm's length. In Chad and its neighbors, however, Qaddafi appears to have found new and potentially fertile fields for planting his Islam-based ideology of direct rule by "the masses."

In the last several months, Libyan activity has been particularly intense in these nearby African countries. Sometimes contacts are friendly, such as the reported training of troops from Guinea, Togo and Benin. But sometimes they are hostile: Charges of meddling in internal affairs have led to breaks in diplomatic relations or expulsion of Libyan envoys by Senegal, Gambia, Ghana, Niger, Mauritania, Equatorial Guinea and Nigeria.

They joined Egypt and Tunisia, already estranged by previous disputes with Qaddafi. Sudan also has had troubles with Libyan support of rebels, but it still maintains relations with Tripoli. At the same time, Khartoum has taken a leading role in condemning Libya's large-scale intervention last month in Chad and its subsequent announcement of a merger with that large central African country. The Sudanese president, Jaafar Nimeri, called yesterday for a summit meeting of African leaders to take whatever steps are necessary to "maintain the independence and unity" of Chad.

Western officials, basing their estimates on satellite reconnaissance, say Qaddafi in the last few weeks has increased the size of his force there to between 6,000 to 7,000 men, backed up by about 100 Soviet-made T54 tanks and Soviet- and Brazillian-made armored personnel carriers, across Chad's 500,000 square miles.

Among those sighted during the decisive battle for the Chadian capital of Ndjamena were non-Libyan African nationals who apparently have joined the Pan-American Legion, a U.S. official said. Some of the black Africans could have been Chadians assigned by Chad's pro-Libyan President Goukouni Queddi as liaison officers, diplomats here pointed out, but the U.S. sources believe at least some of them came as part of the Libyan units.