Baroness Thatcher, the former prime minister, has criticised the allies for not pushing on to Baghdad and destroying Saddam Hussein during the Gulf war.
She also joined Britain's Gulf war commander in criticising the RAF for low level bombing tactics during the 1991 conflict.
Interviewed for the BBC series Gulf War, which will be broadcast in four parts from next Monday, Lady Thatcher criticises publicly her successor, John Major, and the United States government for ending the conflict without bringing down Saddam's regime.
She says: "When you are dealing with a dictator, he has got not only to be defeated, well and truly, but he's got to be seen to be defeated by his own people, so that they identify the privations they've had to go through with his actions. And we didn't do that."
Lady Thatcher also reflects on the irony of her downfall and that of President George Bush, as leaders of the victorious allied countries, while Saddam - who lost - remains in power.
"There is the aggressor, Saddam Hussein, still in power. There is the President of the United States, no longer in power. There is the Prime Minister of Great Britain who did quite a lot to get things there, no longer in power. I wonder who won?"
The former prime minister says she had not thought Saddam likely to attack Kuwait before the invasion.
"We had thought this man has fought a war, against Iran for eight years. During those eight years, something like half a million young people had been killed. Half a million on both sides. Surely after that, he can't go and have another military operation."
She was also astonished at being forced to resign before the end of the war. "I never felt so strongly about anything in my life. I didn't understand it.
"I have no regrets about leaving office; I decided after all to go which I didn't get enough support, but of all the things that I've ever thought of, and I have again, bear no grudge at all, but I thought was astonishing," she says.
Baroness Thatcher echoed comments made by General Sir Peter de la Billiere, the British forces commander in the Gulf at the time, who says in the documentary that he was overruled when he tried to stop low-level bombing.
As a result of the coalition air campaign in January 1991, Lady Thatcher, who was no longer Prime Minister, says that British pilots were lost, causing her deep distress. "I do remember that we had difficulty because, I think it was the Tornados were going in, they had to go in low, and we were losing a pilot a night," she says.
She adds: "I got very upset and said that there's something wrong with the way we are doing this, and let those views be known."
She raised the matter with ministers, but four Tornados were lost in five nights of low level bombing. Four crew members were killed and four were taken prisoner. Two more of the aircraft were lost in the latter stage of the campaign and the Americans lost 27 aircraft.