Nuclear weapons were on board Royal Navy ships dispatched from Gibraltar to the Falklands in 1982, the official history of the conflict reveals.
The book draws on public evidence and secret documents
Professor Sir Lawrence Freedman's book commissioned by the government draws on public evidence and secret documents.
There were no plans to use the depth charges but removal could have delayed the Task Force by 36 hours, he said.
His research also rejects claims that the cruiser the Belgrano was sunk to scupper a possible peace deal.
Three hundred and twenty-three Argentines died in the attack on the Belgrano - the single largest loss of life during the conflict and its most controversial event.
Professor Freedman told BBC Radio 4's Today programme there was "absolutely no truth whatsoever" in the theory.
He said the Belgrano was heading away from the exclusion zone which the UK had imposed around the Falklands.
Initially commanders wanted to sink it because they were worried about a pincer movement.
"Although by the time it was sunk that pincer movement was no longer in train, they wanted it sunk because they were worried about the Argentines' general naval threat and wanted to deter the Argentines," he said.
The Ministry of Defence said in December 2003 that some vessels were carrying nuclear weapons but Professor Freedman's book goes into specific details.
Mrs Thatcher's government was "desperate" to take them off the vessels, but they were trying to make the "biggest diplomatic impact", Professor Freedman said.
"They decided they had better take them and get them off later," he said. "They put them in the safest places possible. There was no intention to use them, but they certainly went."
The frigates Brilliant and Broadsword were each said to be carrying a normal complement of two nuclear depth charges.
Removing the weapons would have caused delays, Prof Freedman says
Ministers opted to store the depth charges on the nuclear weapon-equipped carriers Hermes and Invincible, the book recalls. But the carriers were kept out of Falklands' territorial waters to avoid potential allegations of violation of international law.
Fears over a potential attack eventually lead to the nuclear arms being ordered out of the area.
The 1,102-page two-volume book is the result of eight years of research by Professor Freedman, of the department of war studies at King's College, London.
"My basic objective was to provide an account of what happened that people would trust and not think that I had any sort of political agenda of my own," he said.
The book also covers "poor communications" between different parts of the Task Force which lead to blunders and explores the relationship between the UK and the US during the conflict.
"There was a Pentagon policy which was incredibly supportive of the United Kingdom, giving a lot of material support," he said.
"But the political policy from the Secretary of State and from President Reagan was much more equivocal.
"I think Prime Minister Thatcher found this very hard to take, very hard to understand."