Riot policemen stand guard in front of the residence of Thailand Prime Minister Abhisit Vejjajiva during a protest Monday, April 12, 2010, in Bangkok, Thailand. The Red Shirt protesters are calling for Abhisit to dissolve parliament and step down. Clashes that weekend between anti-government demonstrators and soldiers left 25 dead and more than 800 injured. (Wason Waintchakorn/Associated Press)

For more than two months, thousands of protesters in red shirts were hunkered down in central Bangkok, demanding the resignation of Thailand's government and new elections.

Then in mid-May, the Thai military moved decisively to end the protests.

Two years ago it was protesters in yellow shirts successfully demanding the government's ouster. Now the yellow shirts — that is the royal colour — back the current government.

The red shirts, who seem to have more popular support, are connected to Thaksin Shinawatra, the prime minister overthrown by a 2006 military coup. Although Thaksin is a billionaire, the red shirts are now a mass movement of the poor, mostly from rural Thailand but also with support in the cities.

The yellow shirts have the support of the Bangkok elite, concerned about Thaksin's alleged corruption.

Anti-government protesters are held by Thai soldiers after being arrested from their encampment on May 19, 2010 in Bangkok. (Wong Maye-E/Associated Press)

The division is also geographic, with the yellow shirts enjoying more support in Bangkok and central Thailand, while the north and northeast are red shirt territory.

According to Joshua Kurlantzick of the Council on Foreign Relations in the U.S., "the red shirts represent not just the poor but Thais who feel they've been excluded: excluded from the benefits of globalization, which has worsened Thailand's income inequality; excluded from political decision-making, which is concentrated unhealthily in Bangkok; and excluded from the traditional levers of power — the judiciary, the army, the civil service, and the monarchy, all of which tend to be highly conservative."

Here's a look at how Thailand came to this critical moment:

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Years of monarchy

A unified Thai kingdom was established in the mid-14th century. Thailand is the only Southeast Asian state not colonized by Europeans.

An absolute monarchy ruled the country until 1932, when a bloodless military coup changed the government to a constitutional monarchy. Known as Siam until 1939, the country was renamed Thailand by military dictator Plaek Pibulsongkram. After his defeat at the end of the Second World War, Siam was again the name. Another military coup in 1948 brought Pibulsongkram back to power and a year later the official name was again Thailand.

The military largely ruled the country until the early 1990s, with brief periods of democratic rule.

King Bhumibol Adulyadej, 82, has reigned as constitutional monarch since 1946 and is the world's longest-serving head of state. He was born in the U.S. and educated in Switzerland. The popular but ailing king is known as an accomplished sailor and musician. He is also No. 1 on Forbes magazine's list of "the world's richest royals."

In 1992, mounting public pressure forced the king to appoint an interim prime minister and schedule a parliamentary election for later in the year. It was won by a coalition of parties opposed to military control.

Fourteen years of democratic rule followed, despite a series of scandals, political infighting and the economic downturn of the 1997-98 Asian financial crisis.

In 1994, Thaksin Shinawatra, a prominent businessman, entered the cabinet as foreign minister. In 2001, already facing corruption charges, he became prime minister. His party won re-election in 2005, thanks to the economy's strong performance, the government's handling of the aftermath of the Boxing Day 2004 tsunami, and a health insurance program.

Downfall of the Thaksin government

In February 2006, Thaksin — facing more accusations of corruption and other misdeeds — dissolved parliament and called a snap election for April. But it was boycotted by the three main opposition parties, and their supporters took to the streets, demanding Thaksin's resignation.

A second ballot was held in late April, but it was declared invalid a month later by the country's constitutional court. Thaksin tentatively scheduled a new election for October. It wasn't enough to assuage his critics.

On Sept. 19, 2006, while Thaksin was in New York attending the opening session of the UN General Assembly, the military sent tanks to surround the government's headquarters in Bangkok. A few hours later, retired Lt.-Gen. Prapart Sakuntanak said in a televised address that the government had been dismissed and the 1997 constitution revoked, as the Thai armed forces declared martial law. The generals claimed to have King Bhumibol's support.

In August 2007, the military's constitution was approved, paving the way for new elections to take place in December. The People's Power Party (PPP), formed from the ashes of Thaksin's Thai Rak Thai party, won a plurality of votes and formed a government along with five other parties.

The election and the end of military rule were hailed by many, but the political situation was far from resolved.

Protests in the streets

A series of scandals and missteps brought People's Alliance for Democracy (PAD) protesters, wearing yellow shirts, out into the streets by mid-2008. They denounced the new prime minister, Samak Sundaravej, as a puppet for Thaksin. Samak rode out the storm, surviving the blockades and a parliamentary non-confidence motion. In August, protesters began an occupation of the prime minister's office compound.

Samak's rule was, ultimately, tripped up by a cooking show.

A self-proclaimed foodie, Samak hosted a popular television cooking show — Tasting and Complaining — for seven years before becoming prime minister. When he made several appearances after taking office, however, he broke a constitutional prohibition on private employment while in office.

The country's constitutional court ruled that he had violated the constitution with these appearances, and on Sept. 9, Samak was forced out.

The announcement that Somchai Wongsawat, Thaksin's brother-in-law, would be Samak's successor greatly tempered the protesters' initial euphoria. In the weeks following, government forces continued to crack down on the yellow-shirted anti-government forces, who continued to step up their efforts.

Then, in late November, hundreds of anti-government protesters stormed Bangkok's Suvarnabhumi international airport terminal, forcing officials to halt departing flights. Demonstrators fought running battles with riot police in the city. The airport, a major Southeast Asian hub that handles 13 million tourists each year, cancelled all departing flights as a result. About 4,000 travellers, including Canadian celebrity chef Michael Smith, were stranded.

Thailand's Prime Minister Abhisit Vejjajiva arrives at Parliament Wednesday, April 7, in Bangkok, Thailand. (Associated Press)

As the airport siege continued, army chief Gen. Anupong Paochinda added his voice to the fray, calling on the government to hold new elections. In a televised statement, Somchai said he would continue to govern for the "good of the country." PAD protesters forced the closure of Bangkok's other airport.

Democrats take over

Days after his pledge to stay in power, Somchai was forced out after a constitutional court found the PPP to be in violation of election law. A new coalition was brokered, in part by the military, and the parliament chose Abhisit Vejjajiva of the Democrat party as prime minister Dec. 15. The Democrats are aligned with PAD.

Abhisit, 45, is from an elite Bangkok family. He was born in England and returned there to study at Eton and Oxford. He has tried to win the support of Thaksin's rural and poorer supporters, without much success.

Red shirt protests, 2009

In March 2009, it was the red shirts' turn to take to the streets. They did so in the thousands, under the umbrella of the United Front for Democracy against Dictatorship (UDD). Thaksin was accused of encouraging the protests through nightly speeches, and even bankrolling them from exile.

After days of mounting tensions, the situation exploded on April 13.

In a series of rolling street battles, buses were set on fire and used to barricade intersections in Bangkok. Firebombs were thrown at Thai troops, who returned fire with tear gas and shot automatic weapons over the protesters' heads. At least two were reported killed in the clashes and more than 120 injured.

UDD leaders ended their protest the next day and the Thai government reported that order had been restored to the streets. Several protest leaders were taken into police custody.

Red shirt protests continued sporadically over the next months. There were also smaller yellow shirt protests.

Anti-government protesters and supporters of ousted Prime Minister Thaksin Shinawatra fill up the street on March 28, in Bangkok, Thailand. (Apichart Weerawong/Associated Press)

Meanwhile, an insurgency in the predominantly Malay Muslim south of Thailand has led to more than 3,900 deaths in the last six years.

Red shirt protests, 2010

On March 14, about 100,000 protesters marched in Bangkok to demand the Abhisit government resign and new elections. Later in the week, the red shirts tossed human blood at the prime minister's office, his residence and Democrat Party headquarters.

Televised talks between Abhisit and protest leaders at the end of March went nowhere, as protests continued.

After protesters briefly stormed the Thai parliament, the government declared a state of emergency on April 7. The red shirts defied the edict. The government blocked the signal of the opposition's TV station and censored content from at least 36 websites, including material from Twitter and YouTube.

More protests forced authorities to allow the TV station to resume broadcasting while tensions continued to escalate.

Thai security forces fire rubber bullets at anti-government demonstrators during a clash Saturday, April 10, in Bangkok, Thailand. (Wason Waintchakorn/Associated Press)

On April 10, the fifth consecutive weekend of protest brought the worst political violence in Thailand in almost 20 years: 21 protesters and soldiers died, and almost 900 were wounded before the military backed off.

The next day, momentum seemed to swing further in favour of the red shirts. The election commission recommended the governing Democrat Party be dissolved for electoral fraud and the armed forces chief seemed to moving away from continued support for the government.

"If the issue cannot be resolved through political means, then Parliament dissolution seems to be a reasonable step," Gen. Anupong Paochinda told a press conference.

The standoff continued for several weeks and then the government offered to hold early elections in November if the red shirts would end their occupation.

The red shirts accepted the election proposal but wanted the official then in charge of security operations, Deputy Prime Minister Suthep Thaungsuban, held accountable for the deaths and violence on April 10.

Detecting some division in the protest leadership, the government rescinded their election offer and stepped up efforts to force an end to the occupation of central Bangkok, according to The Bangkok newspaper, The Nation.

At that point, the head of the red shirts' paramilitary arm, a former general known as Sae Daeng, was shot by a sniper while talking to foreign correspondents on May 13. The sniper has not been identified.

The next day the military again moved to oust the protesters, resulting in the bloodiest day of violence since April 10.

On May 19, the military succeeded in forcing the red shirts from their encampments around Bangkok. But the city was in smoke and flames. About 40 buildings were burning.

Most red shirts leaders surrendered or were arrested. Anti-governments radio stations were raided by soldiers, their broadcasting terminated.

The state of emergency continued until December.