Top secret plans for attacking Iraq were drawn up five months before the war started, a court martial has heard.
Training UK troops for Iraq began late, the hearing heard
US defence planners passed plans, with codenames such as P-Day, A-Day and G-Day, to UK army bosses in October 2002.
The war against Saddam Hussein was launched on 20 March, 2003, in a series of US air strikes.
The plans were revealed during the court martial of reservist Lance Corporal Ian Blaymire, charged with the manslaughter of a colleague in Iraq.
Reservist Sergeant John Nightingale, 32, from Guiseley, West Yorkshire, died after being hit in the chest at point-blank range by a bullet from an A2 rifle at Shaibah, near the southern city of Basra on 23 September last year.
Blaymire, 23, of Leeds, is appearing at a court martial at Catterick Garrison, North Yorkshire, charged with his manslaughter.
The secret documents were compiled by Lt Colonel Christopher Warren, staff officer at Land Command, Wiltshire, who was responsible for operational training at the time of the conflict, the court martial heard.
P-Day stood for the date on which US President George Bush would make a decision for going for war, he revealed.
That date was pencilled in for 15 February, 2003.
A-Day stood for the beginning of the air strikes, scheduled for the first week of March 2003, while G-Day stood for the start of the ground offensive, due to start two days later.
The dates and codenames were only revealed after the court martial was adjourned for several hours for legal argument.
Assistant Judge Advocate Paul Camp eventually ruled the press and public had a right to hear the evidence.
Army chiefs wanted training for the conflict to begin at the start of December 2002 but this was delayed because of "sensitivities", Tuesday's hearing was told.
Mr Warren had sent the plans to the Defence Crisis Management Organisation in London - the "political, military interface at the highest level" - which had vetoed them.
The hearing was told training for the Territorial Army began two months late while regular army training was a month late.
When asked why training had not begun on time Mr Warren told panel members army chiefs had "no political authority to start it".
The "sensitivities" that caused the Defence Crisis Management Organisation to veto the planned training start dates were because of the "world interest" in the developing situation with Iraq at the start of December, he said.
"If the UK had mobilised whilst all this was going on that would have shown an intent before the political process had been allowed to run its course."
The hearing continues.