Below are some facts about the red-shirted United Front for Democracy against Dictatorship (UDD), which is demanding the military backs off and Prime Minister Abhisit Vejjajiva calls an immediate election.
• The red shirts are made up mainly of members of the rural poor and urban working classes. Many are supporters of the fugitive, twice-elected former Prime Minister Thaksin Shinawatra, to whom they remain loyal because of his mold-breaking populist policies while in office from 2001-2006.
• They say they are fighting against intervention in politics and the judicial system by unelected conservative elites, who they accuse of operating with impunity and conspiring to topple democratically elected governments.
• The UDD believes the 2006 coup against Thaksin, his graft conviction in absentia and the dissolution of his Thai Rak Thai Party and its next incarnation, the People's Power Party (PPP), were all masterminded by his influential opponents.
• Thaksin, an ex-telecoms tycoon accused by his opponents of being an autocratic crony capitalist disloyal to the monarchy, is widely assumed to be the de facto boss and main financier of the UDD. But it has at least 20 members oon it leadership council, several of whom have served in Thaksin's parties or have a history of pro-democracy activism.
• Among them are Jatuporn Prompan and UDD chairman Veera Musikapong, politicians and former activists who rallied against a military dictatorship in 1992. Jatuporn is a currently a lawmaker in the pro-Thaksin opposition party, Puea Thai. Veera, one of the more moderate leaders, has been missing for almost a week, with speculation he fled to England when a peace deal collapsed.
• Accomplished UDD speaker Nattawut Saikua is a former government spokesman under the PPP. Left-wing activist and rural doctor Weng Tojirakarn has emerged as a prominent leader, as has well-known singer Arisman Pongruangrong.
• Even red shirt leaders say moderates and hard-liners disagree about whether to accept a deal and end the rally or fight to the end.
• The movement's security chief Khattiya Sawasdipol, a renegade army specialist, was the victim of an assassination attempt on Thursday in what analysts said was a move to decapitate the UDD's military leadership. He underwent brain surgery and was in a critical condition.
• The red shirts have proved to be a well-organized and powerful extra-parliamentary force, holding regular protests in Bangkok and in their northern and northeastern strongholds, which attract tens of thousands of people, lasting days, if not weeks.
• They occupied the headquarters of the government for three weeks in April 2009 and simultaneously shut down a summit of Asian leaders two hours away in the beach resort of Pattaya.
• They have occupied a site covering roughly 3 sq km (1.2 sq mile) of a luxury hotel and shopping district for a month in an eight-week protest that reached its peak on March 14 with 150,000 protesters, most flooding into Bangkok from far-flung provinces.
• The UDD has scores of "politics schools" across the country and organizations at national, provincial, district and village levels, responsible for fund-raising and recruiting.
• The group has its own television channel, magazine, websites, radio stations, merchandise shops and music album. Red shirts also carry their own UDD identification cards. Protest sites have masseuses, infirmaries, showers, canteens and dozens of vendors selling snacks, cigarettes, T-shirts and coffee.
• The movement has hundreds of "red shirt guards" to provide security at rallies. Their current protest at the Rachaprasong has been fortified at nine entrances by concrete blocks, wooden spears, razor wire and tires doused in petrol.
• Although most of the UDD's protests have been peaceful, the red shirts have earned a reputation for violence after numerous face-offs with troops and police in the last 14 months.
• Hundreds of red shirts have been skirmishing with troops across Bangkok's business distrct since Thursday night, when the military began trying to set up a security cordon around their encmapment, firing homemade rockets, and hurling rocks and petrol bombs. Some fired guns, witnesses said. So far, 46 people have been killed and about 1,500 wounded since the protest began.
• In April 2009, they stormed the Interior Ministry and attacked a vehicle they thought was carrying Abhisit. A day later, a few hundred hard-core demonstrators occupying two Bangkok intersections set buses ablaze, hijacked petrol tankers and hurled Molotov cocktails and rocks at troops.
• A rally in Bangkok's historic heart turned bloody on April 10, when a bungled effort by troops to evict protesters killed 25 people and wounded more than 800, including many soldiers.
• Deadly and still-unexplained grenade attacks on April 22 and May 7 in Bangkok's Silom business district have been widely blamed on the red shirts, further denting their reputation, as did their April 28 skirmishes with security forces on a suburban highway in which a soldier was killed.
• The presence of shadowy, black-clad gunmen during the April 10 clashes shows the red shirts have a paramilitary arm, to add to their estimated 1,000 guards. The UDD says it does not know who the mysterious assailants are. The government believes the UDD has hundreds of assault rifles and grenade launchers stashed away, many stolen from fleeing troops during the riot.
