There were four more explosions in London [Images] on July 21, 2005, but of a much lower intensity as compared to those of July 7. The target again was the public transportation system. As on July 7, there were three explosions in the underground railway system and one in a bus. Apart from injuries to one person, no other human casualty has been reported. Material damage was also very little as compared to July 7.

What caused the explosions? The answer is not yet clear. In their first press conference on the explosions, the British police expressed the view that the blasts were meant to cause large casualties, but they did not because in all the four instances the Improvised Explosive Devices (IED) failed to function.

An IED generally consists of a quantity of explosives known as the explosive charge, a detonator, which causes the explosive charge to explode, and a mechanism for activating the detonator. The activation could be done through a mechanical or a chemical timer or through a remote control. In the case of a human bomb, the terrorist carries the explosive charge and the detonator on his person and activates the detonator himself.

According to the police version, it would seem that while the perpetrators of the blasts activated the detonators, the detonation, which caused the bang of low intensity, failed to cause the connected explosives to explode. Had the devices exploded as they were designed to, the casualties and the property damage would have been heavier.

Unsatisfactory assembling of the IED with incorrect connections can lead to a failure of the explosive, but it is somewhat intriguing that all the four IEDs should have failed to explode. If this ultimately turns out to be correct, this would show that the same person assembled all the four IEDs and, while doing so, he committed the same mistakes in making the explosives. Extraordinary, but it could happen.

This indicates the possibility that the person who assembled the IEDs of July 7 which exploded successfully, was different from the person who assembled those of July 21. The British police's surmise is that suicide volunteers were also involved on July 21, but they managed to escape -- possibly with the injuries caused by the detonation -- after discarding the rucksack containing the failed explosive charge.

The abandoned rucksacks should enable the police to identify -- more conclusively than on July 7 -- the explosive material used (acetone peroxide?). At least five persons should have been involved in the explosions of July 7 -- the person who fabricated the explosive charge and assembled the IEDs and the four suicide volunteers. An equal number should have been involved on July 21.

Apparently, the investigations made by the police so far into the blasts of July 7 had not led them on to the trail of those responsible for the blasts of July 21. This could be due to their poor sources in the local Muslim community and the failure of knowledgeable members of the Muslim community to come forward with information they know. Another possibility is that the two groups were operating autonomously of each other -- not knowing the identities of each other.

This is what has been happening in Iraq -- a number of well-motivated groups operating autonomously of each other are unaware of the identities of each other. As a result, the capture of one group or any of its members does not automatically lead the US troops on to the trail of others.

The most worrisome indicator of the July 21 blasts is that there is an unknown number of well-motivated and well-trained terrorists in different parts of the UK. They either form part of a single large group or are operating autonomously in many small cells. They could reduce the UK to a mini Iraq.

As happened last time, the British police would try this time too to identify the four perpetrators with the help of the closed circuit films, but this task could be more difficult this time. After July 7, they recovered the films plus the identity documents of the perpetrators from the scene. Matching the visuals on television films with the pictures on the documents would have been easy. This time, they do not have any identity documents to go by.

However much Prime Minister Tony Blair [Images] and Foreign Secretary Jack Straw may deny it, it is fairly certain that the explosions of July 7 and 21 were reprisal attacks for the British role in the invasion and occupation of Iraq and more particularly for the British assistance to the American troops in the Falluja operation last year.

Using their Air Force and armour, the Americans literally reduced Falluja to ruins. Before they started their operation for the pacification of Falluja, a British Army unit had been moved into the Sunni Triangle from Basra to seal off the likely escape routes of the Iraqi Sunnis caught up in the American offensive.

Since the occupation of Iraq by the US-led coalition, this was the first time the British troops were involved in a ground operation in support of the Americans in the Sunni Triangle. The US-UK operation to subdue Falluja was compared by many to the Anglo-American air strikes for three nights in succession on Dresden in Germany [Images] towards the end of the Second World War. Allegedly to punish the German people for supporting the Nazis, the Anglo-American air strikes reduced Dresden to rubble, killing thousands of German civilians.

The jihadi desire to avenge the British role in Iraq had redoubled ever since the Falluja operation and it remains very strong. In Spain, the Madrid blasts of March 11, 2004, were not followed by any more incidents because of the success of the Spanish police in identifying and arresting all those involved and the decision of the newly-elected Spanish government to withdraw the Spanish troops from Iraq.

In the UK, the fact that the British police have not had the same success so far as the Spanish police and the firm reiteration by the Blair government of the correctness of its policies relating to Iraq make it a target in the hope of bringing the government more under public pressure to change its Iraq policies.