"The U.S. nuclear umbrella alone is no longer enough to assure our security, " says Defense Minister Yoshinori Ohno.
In return, America could extend a nuclear umbrella to Israel to put it at ease about nuclear attacks.
Like some European states, Britain could limit itself to defending its national territory while sheltering under NATO and America's nuclear umbrella.
Until now, both countries have nestled under the U.S. nuclear umbrella.
The U.S. provides a nuclear umbrella for 30-plus countries, including several -- Japan, Germany and South Korea, for example -- capable of developing their own nuclear weapons.
Kristensen says that during the Cold War, Japan faced a tough choice between seeking national security under the U.S. nuclear umbrella and telling the public the truth.
Lord Robertson, a former Nato secretary general, has called Germany "irresponsible" for wanting to remain under America's nuclear umbrella while exporting the obligation of maintaining it to other European states.
For another, developed nations that have in the past been willing to entrust their security to the protection of the American nuclear umbrella will probably feel obliged to revisit that decision.
First, advanced and generally friendly countries -- like Germany, Japan and South Korea -- that refrain from acquiring nuclear weapons in part because they trust the American nuclear umbrella to protect them.
Even if the Kremlin dropped its historic opposition to limiting these arms in a new accord, verification would be impossible as a practical matter and the price high in terms of further reducing the "nuclear umbrella" U.S. tactical nukes provide our allies.
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The third reason for our deterrent is that it would prevent a cascade of proliferation because of the nuclear umbrella that the United States provides for over thirty-one countries, including many with the technology and resources for the development of nuclear deterrence on their own.
U.S. nuclear submarines ply the region's waters, however, and Washington makes clear that its so-called nuclear "umbrella" over South Korea is meant to deter an attack on its ally by North Korea, whose 1950 invasion ignited the three-year Korean War.
In a little-noticed report sent to Congress in February, the National Intelligence Council, an umbrella panel representing U.S. spy agencies, detailed the threat posed by stored Russian nuclear weapons.
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