Iran justified arresting the British crew because the U.S.arrested five members of the Islamic Revolutionary Guard Corps in Erbil in Northern Iraq on January 11.
http://www.time.com/time/world/article/0,8599,1604546,00.html
The British sailors and marines that were being held by Iran were ambushed at their most vulnerable moment, while climbing down the ladder of a merchant ship and trying to get into their bobbing inflatables. It took only three minutes for the Iranians, moving at 40 knots, to move from their legitimate positions monitoring shipping in their waters to come alongside the British
http://www.timesonline.co.uk/tol/news/world/middle_east/article1582544.ece
http://www.jihadwatch.org/archives/015783.php
http://www.timesonline.co.uk/tol/news/world/middle_east/article1530527.ece
http://news.yahoo.com/s/ap/20070331/ap_on_re_eu/british_seized_iran_226
Various news media reported....
Fifteen British sailors taken at gunpoint Friday by Iranian Revolutionary Guard and Al Quds soldiers were captured intentionally and are to be used as bargaining chips to be used for the release of five Iranians who were arrested at the Iranian consul in Irbil, Iraq by US troops, an Iranian official told the daily paper Asharq al-Awsat on Saturday.
In addition, a senior Iranian military official said Saturday that the decision to capture the soldiers was made during a March 18 emergency meeting of the High Council for Security following a report by the Al-Quds contingent commander, Kassem Suleimani, to the Iranian chief of the armed forces, Maj.Gen. Hassan Firouz Abadi. In the report, according to Asharq al-Awsat, Suleimani warned Abadi that Al Quds and Revolutionary Guards' operations had become transparent to US and British intelligence following the arrest of a senior Al Quds officer and four of his deputies in Irbil.
The first sign of a possible campaign against high-ranking Iranian officers emerged earlier this month with the discovery that Ali Reza Asgari, former commander of the Revolutionary Guard’s elite Quds Force in Lebanon and deputy defence minister, had vanished, apparently during a trip to Istanbul.
Asgari’s disappearance shocked the Iranian regime as he is believed to possess some of its most closely guarded secrets. The Quds Force is responsible for operations outside Iran.
Last week it was revealed that Colonel Amir Muhammed Shirazi, another high-ranking Revolutionary Guard officer, had disappeared, probably in Iraq.
A third Iranian general is also understood to be missing — the head of the Revolutionary Guard in the Persian Gulf. Sources named him as Brigadier General Muhammed Soltani.
As fantastic an idea as that may seem, it may indeed be in reality behind the politics of Iran. Iranian president Ahmadi-nejad is a mahdaviat (one who believes in and prepares for the mahdi) The mahdi is the divinely guided one who appears to lead Muslims during a time of chaos. Ahmadi-nejad spent $17 million of Iran's money to remodel the Jamkaran mosque in Qom in preparation for the arrival of the mahdi.
If Iran provokes a war and the mahdi arrives then Iran was instrumental in doing it. If Iran provokes a war and the mahdi does not arrive but a lot of Iranians die then they will all go to jannah (heaven) because they have died in the jihad fee sybil Allah (jihad for Allah).
http://www.youtube.com/watch?v=Z_H7af26_Gk
Even if no military action ensues, then Iran has gained respect in the Muslim world for standing up to the West.