While the protests convulsing Bahrain and Libya this past week occurred in vastly different contexts - and will likely produce very different results - both were met with conspicuously swift crackdowns. And in both cases, reports suggest the Libyan and Bahraini regimes deployed foreign fighters and mercenaries against their own citizens, lethal clashes that left scores wounded and many dead.

Though difficult to substantiate in the current chaos, reports from eastern Libya, in particular from the city of Benghazi, claim that snipers and militiamen from sub-Saharan Africa gunned down residents on the streets. The Dubai-based al-Arabiya network says some of the guerrillas were Francophone mercenaries recruited by one of the sons of dictator Muammar Gaddafi. Qatar-based al-Jazeera detailed pamphlets circulated to mercenary recruits from Guinea and Nigeria, offering them $2,000 per day to crack down on the Libyan uprising. And, as further reports of defections from the Libyan military filter in, the cornered Gaddafi regime may turn more and more to hired guns from abroad. On television channels and Twitter, frantic rumors circulated about Gaddafi preparing for a mercenary-backed counteroffensive against his opponents. (See pictures of the rise of Libya's Colonel Gaddafi.)

While the violence appears to have pushed Libya to a tipping point, protests in Bahrain slackened after a week of bloody confrontations between demonstrators and the country's security forces. Sectarian tensions underlie the unrest, with the tiny island kingdom's Sunni Muslim monarchy pitted against the country's predominantly Shi'ite population. A significant segment of the state's security personnel are Sunnis brought in from countries like Syria, Iraq, Jordan and Pakistan to buttress the ruling dynasty's authority. It's a policy that Shi'ites say is symbolic of widespread institutional discrimination in Bahrain, and it played a key role in clashes earlier this month when uncompromising - and often foreign - security forces violently dispersed protesting crowds, killing at least six.

The popular outrage surrounding the use of these foreign soldiers in the crackdowns isn't surprising, but it's only in the past century that the armies of most of the world's nation-states have actually reflected the demographics of their countries. For centuries before, most militaries contained whole regiments of mercenaries and roving soldiers of fortune and were often staffed by officers from foreign lands. The term freelance - now a feature of journalistic lingo - still carries its original martial connotation from a time when companies of fighting men raised their blades in the service of the highest bidder. (See the top 10 famous protest plazas.)

Foreign warriors were valued by monarchs wary of their own restive populations and the rivalries and jealousies of local nobles. The great empires of the Middle East all boasted a rank of soldiers drawn (or abducted) from abroad. The Ottomans had the janissaries, mostly young Christians from the Caucasus and the Balkans, who converted to Islam and were reared from an early age to be the Sultan's elite household troops, often forming a powerful political class of their own in various parts of the empire. Elsewhere, the Mamluks, slave warriors from Africa to Central Asia forced into service by Arab potentates, managed to rule a large stretch of the modern Middle East from Egypt to Syria for some 300 years, repulsing the invasions of European crusaders as well as the Mongol hordes.

The most famous troupe of foreign fighters to take up arms in the Middle East was the French Foreign Legion, formed in the 19th century to be the vanguard of France's imperial adventures overseas. To this day, no outfit of mercenaries attracts the sort of admiration that the legionnaires still do, remembered as the romantic heroes of Beau Geste, a motley pan-European crew braving the wild winds and natives of the North African desert. In reality, the legionnaires, a large number of whom had criminal records, bore a fearsome reputation for violence. One recruit in the 1950s described his compatriots as "panting Dobermans, desperate to be let loose amongst a Muslim crowd which they can tear apart with the fans of their machine guns." The legionnaires were present at some of France's most traumatic defeats in Indochina and Algeria and, though they still exist, their star has dimmed with France's much diminished empire. (Read "European Arab Immigrants Watch Protests Skeptically.")

Meanwhile, a handful of British mercenaries in the Middle East left a far more indelible legacy, with none of the glory attached to the French Foreign Legion. The oil-rich Gulf states eagerly snapped up former British soldiers to help defend their kingdoms from the advances of socialists and other insurgents, often with London's tacit backing if not direct consent. In the 1960s, Qatar's feared chief of police was Ronald Cochrane, an ex-cop from Glasgow who assumed the name Mohammad Mahdi. Other British soldiers made their way into guerrilla campaigns from Malaya to Angola, enmeshed often in tangled proxy conflicts spawned by the Cold War. One English mercenary, a man identified by a 1972 television crew as Major Ray Barker-Scofield, described his patch of turf in a remote corner of Oman where he was fighting guerrillas on behalf of the government as "the last place in the world where an Englishman is still called a sahib" - in other words, his gig as a mercenary reminded him of the good old days of the British Empire.