The United States will withdraw 60,000 to 70,000 troops from Europe and Asia over the next decade, President George W. Bush said Monday as he announced the biggest military reorganisation since the end of World War II.
Bush added that about 100,000 civilian employees and families of soldiers would also be affected by the huge changes.
The president gave no details, but US officials have said Europe, particularly Germany, will be most affected by the redeployments.
"For decades America's armed forces abroad have essentially remained where the wars of the last century ended in Europe and in Asia," Bush said at a conference of US veterans in Cincinnati as he presses his campaign for the November 2 presidential election.
"America's current force posture was designed, for example, to protect us and our allies from Soviet aggression. The threat no longer exists."
He added: "Over the coming decade, we'll deploy a more agile and more flexible force, which means that more of our troops will be stationed and deployed from here at home.
"We'll move some of our troops and capabilities to new locations so they can surge quickly to deal with unexpected threats. We'll take advantage of 21st-century military technologies to rapidly deploy increased combat power.
The new plan "will help us fight and win these wars of the 21st century. It will strengthen our alliances around the world while we build new partnerships to better preserve the peace."
Bush said that US officials "will bring home about 60,000 to 70,000 uniformed personnel and about 100,000 family members and civilian employees."
He promised the United States would retain "a significant presence overseas," but also that the changes "will reduce the stress on our troops and our military families."
Bush said there would be savings "as we consolidate and close bases and facilities overseas no longer needed to face the threats of our time and to defend the peace."
The United States has been working on the reorganisation for more than three years.
Defence Secretary Donald Rumsfeld has stepped up calls for change since the September 11, 2001 attacks on New York and Washington which unleashed the US "war on terror".
Wars in Afghanistan and Iraq have left the US military stretched to find enough forces.
And Rumsfeld said Sunday that the United States planned to shift US troops out of Germany and northern Europe as part of the repositioning. He briefed Russian Defence Minister Sergei Ivanov on the plans over the weekend.
"There will be a shift from Germany, and we've talked to Germany about that, and some numbers," Rumsfeld said. The United States will continue to have bases in Germany, he said.
The United States has about 100,000 troops deployed in Europe and about the same number in Asia, outside Iraq and Afghanistan. There are about 70,000 troops in Germany, 37,500 in South Korea and 48,000 in Japan.