Timeline: 2010 crisis on the Korean peninsula

26th March: The Cheonan, a Republic of Korea Navy (ROKN) corvette sailing close to the disputed inter-Korean maritime border, sank after an explosion split the vessel in two. Fifty-eight sailors manage to escape but another forty-six were killed.

27th March: As the ROKN continued its search for survivors, South Korea's president, Lee Myung-bak, calls emergency security meetings and orders an investigation into the sinking. With speculation mounting of a possible North Korean torpedo attack, South Korea's Defence Minister indicated to Parliament that the authorities would undertake a full investigation. It was also emphasised that it was still too early to connect the sinking of the ship to North Korea.

30th March: Whilst still not blaming the North directly for the explosion, South Korea's Defence Minister, Kim Tae Young, speculated that the Cheonan may have been hit by Soviet mines laid during the 1950-53 Korean War. The possibility of an accident involving the torpedoes, missiles and depth charges with which the Cheonan was armed was also not ruled out.

1st April: After initially ruling out the possibility of a North Korean attack on the Cheonan, South Korea's government begins to subtly shift its stance. Despite intelligence reports indicating no 'unusual trends' in North Korean military movements, government officials speculate of a 90% likelihood that the North was behind the attack.

6th April: South Korea's main opposition party called for the country's top military leaders to be sacked for last month's naval disaster. The opposition also called for the resumption of dialogue and humanitarian aid for the North. As rumours continued that the Cheonan was struck by a torpedo the opposition also called for a parliamentary investigation and demanded that the survivors give their account.

12th April: An international team of experts is assembled to begin the investigation into the sinking of the Cheonan. British, Australian, Swedish and Canadian experts join and team of American and South Korean investigators. President Lee indicated that the team were to become part of a 'very objective investigation' whose findings cannot be disputed. The President also continued to caution against blaming the North.

16th April: After the stern of the Cheonan was recovered a top investigation official told a news conference that an outer explosion was the most likely cause of the sinking. After a visual inspection Yoon Duk-yong indicated that the twisting of the metal from the stern had been caused by an outside blast. He also indicated that the Cheonan was halved in the middle, making it increasingly likely that it was hit by a torpedo fired from a submarine or a mine.

18th April: The stern of the Cheonan arrives to its home port. Divers also successfully tied a third chain around the bow of the ship. After attaching a final link it was anticipated that the rest of the wreckage would be lifted later in the week. Up until this point, preliminary investigations suggested that a sea mine or torpedo was responsible for the explosion. With the split point located near the centre of the vessel investigators begin giving more credence to a torpedo attack. However military officials indicate that debris assumed to be from a torpedo has yet to be found by investigations.

20th April: Investigators provide evidence suggesting that a torpedo or mine was responsible for the blast that sunk the Cheonan. Kim Tae-young told the National Assembly's Defence Committee that investigations pointed to an external blast as the most probable cause of the sinking. The civilian-military investigation team also said that it had gathered 155 pieces of debris from the Cheonan which it was now classifying.

22nd April: The Korea Herald reported that immediately after the Cheonan sinking a military intelligence agency suggested to the Defence Ministry that North Korea was 'definitely responsible' for the incident. The agency also reported that the vessel was struck by a 200-kilogramme torpedo fired from a submarine. However the Government refused to confirm whether such a security report was made.

23rd April: South Korea indicated that it had no plans to launch a revenge attack against the North if it turns out that it sank the Cheonan. President Lee told journalists that as the investigation was being conducted with international cooperation, the international community was also central to taking necessary measures when investigation results were confirmed.

5th May: The sinking of the Cheonan prompts a rethinking of South Korea's military strategy. In a meeting with President Lee, Kim Tae-young confirmed that the South will shift from attempting to thwart a full scale conventional attack from North Korea to dealing with limited, unconventional acts of aggression. On the same day North Korea completed a deployment of 50,000 special forces along the border with the South.  This deployment actually began two or three years ago.

9th May: South Korea's Defence Minister confirms that traces of RDX explosive was found on the wreckage of the Cheonan and in sand collected from the seabed. The discovery indicates that the vessel was probably struck by a torpedo.

15th May: The ROKN fire warning shots at North Korean vessels crossing the Northern Limit Line of the disputed maritime border. No casualties were reported.

20th May: An international investigation team concluded that a North Korean submarine torpedo was responsible for the sinking of the Cheonan. Investigators said that they had discovered part of the torpedo on the sea floor carrying North Korean lettering. This matched lettering on a North Korean torpedo found by the South seven years ago. The North branded the claim as 'fabrication' and threatened war if sanctions were imposed.

24th May: South Korea's Defence Ministry confirms the resumption of psychological broadcasts across the border. This involved the reactivation of 94 loud speakers to deliver news and music to North Korean soldiers and local villages. In addition to broadcasts South Korea also reactivated electronic billboards and planned to drop leaflets over North Korean airspace. The North is expected to engage in its own broadcasts warned South Korea that it would be held responsible of the 'destructive consequences' of its psychological warfare.

25th May: North Korea cuts all relations with the South. The North also expelled all South Korean workers from a jointly-run factory, severed communication ties and banned ROK ships and planes from territorial waters and airspace. North Korea also accused the South of illegally entering its territorial waters. As a result the North vowed to put into force 'practical military measures to defend' its territory.

26th May: Asia's equity markets suffered as the Korean peninsula crisis sent stocks plummeting to ten-month lows. Fears that North Korea was preparing for military conflict particularly affected stocks in financial companies and carmakers. However defence stocks continued to perform well amid the geopolitical tensions.

27th May: North Korea scraps a bilateral agreement aimed at preventing accidental clashes with the South in the West Sea of Korea. The move came as the ROKN staged a major anti-submarine exercise, its first show of strength since tensions flared.

The UK Defence Forum's own analysis of the crisis on the Korean peninsula can be read here.