Military commanders are expected to tell the inquiry into the Iraq war, which opens on Tuesday, that the invasion was ill-conceived and that preparations were sabotaged by Tony Blair's government's attempts to mislead the public.

They were so shocked by the lack of preparation for the aftermath of the invasion that they believe members of the British and US governments at the time could be prosecuted for war crimes by breaching the duty outlined in the Geneva convention to safeguard civilians in a conflict, the Guardian has been told.

The lengths the Blair government took to conceal the invasion plan and the extent of military commanders' anger at what they call the government's "appalling" failures emerged as Sir John Chilcot, the inquiry's chairman, promised to produce a "full and insightful" account of how Britain was drawn into the conflict.

Fresh evidence has emerged about how Blair misled MPs by claiming in 2002 that the goal was "disarmament, not regime change". Documents show the government wanted to hide its true intentions by informing only "very small numbers" of officials.

The documents, leaked to the Sunday Telegraph, are "post-operational reports" and "lessons learned" papers compiled by the army and its field commanders. They refer to a "rushed" operation that caused "significant risk" to troops and "critical failure" in the postwar period.

One commander said the government "missed a golden opportunity" to win support from Iraqis. Another commented: "It was not unlike 1750s colonialism where the military had to do everything ourselves". One, describing the supply chain, added: "I know for a fact that there was one container full of skis in the desert".

Some troops were deployed in civilian flights to countries neighbouring Iraq with their equipment "brought in by hand baggage". Items considered dangerous, including penknives and nail scissors, were confiscated from them.

Interviewed for the postwar report drawn up by the MoD, Brigadier Bill Moore, commander of 19 Brigade, was asked: "Did you receive the correct level of advice for the nation-building you faced?" He replied: "We got absolutely no advice whatsoever. The lack of advice from the FCO [Foreign and Commonwealth Office], the Home Office and DFID [the Department for International Development] was appalling."

The "lessons learned" report stated: "Never again must we send ill-equipped soldiers into battle". However, many of the failures recounted in leaked documents and given in evidence to Commons committees, notably relating to equipment, were repeated in Afghanistan as inquests have shown.

Significantly, the documents support what officials have earlier admitted – that the army was not allowed to prepare properly for the Iraq invasion in 2002 so as not to alert parliament and the UN that Blair was already determined to go to war.

The documents add: "In Whitehall, the internal operational security regime, in which only very small numbers of officers and officials were allowed to become involved [in Iraq invasion preparations] constrained broader planning for combat operations and subsequent phases effectively until Dec 23 2002."

Blair had in effect promised George Bush that he would join the US-led invasion when, as late as July 2002, he was denying to MPs that preparations were being made for military action. The leaked documents reveal that "from March 2002 or May at the latest there was a significant possibility of a large-scale British operation".

Documents leaked in 2005 show that, almost a year before the invasion, Blair was privately preparing to commit Britain to war and topple Saddam Hussein, despite warnings from his closest advisers that it was unjustified. They also show how Blair was planning to justify regime change as an objective, despite warnings from Lord Goldsmith, the attorney general, that the "desire for regime change was not a legal base for military action.

Chilcot says he and his team would not shrink from making criticisms of individuals or organisations if they were justified. But he stressed the inquiry was not a court of law set up to determine issues of guilt and innocence.