Today's release of more than 400,000 secret files on the American-led war in Iraq is the biggest single military leak in US history.

It dwarfs Wikileaks' publication earlier this year of 77,000 secret logs of the war in Afghanistan.

Much of what is contained in the files is confirmation of things we already know in a conflict that, unlike Afghanistan, now bears little resemblance to when the reports were first compiled.

The bulk of the new documents, thought to have been leaked by a US soldier in Iraq, are known as SIGACTS, or "significant activity logs". The reports are filed by officers in their hundreds each day and can cover something as mundane as distant rifle fire to major military operations such as the movement of personnel or deals with tribal figures and informants.

Much attention will be paid to allegations of torture in jails, ministries and "black sites" run by Iraqis themselves – something which has received less coverage than coalition abuses like Abu Ghraib. There is also likely to be fresh revelations about incidences of civilian casualties that were not discovered by Iraqi or foreign media, as well as potentially damaging items on the reach of regional powers such as Iran.

When Wikileaks released their Afghan war logs earlier this year, senior figures in the US and British military warned that it would risk the lives of troops on the ground.

Wikileaks argues that the public interest in releasing historical documents about a deeply controversial war far outweighs any risk caused by their publication. They accuse Coalition forces of using scaremongering to try to persuade news outlets not to reprint the dossiers.

A secret memo obtained by the Associated Press last week revealed that even the Pentagon has concluded that no US intelligence sources or practices were compromised by the posting of the secret Afghan war.

Staffed by committed Freedom of Information activists, many of whom are politically opposed to the US-led conflicts in Iraq and Afghanistan, Wikileaks has revelled in its newfound notoriety and persona non grata status within the US establishment.

However, allegations made by human rights organisations that the Afghan war logs risked the lives of Nato informants has caused some consternation among its activists and allies.

For the Iraq dossiers, Wikileaks and its media allies have redacted names where they believe specific individuals may be at risk. The US military, meanwhile, says it is on standby to inform any Iraqis who may be outed as working with the coalition in the files.