I don't fear any country, religion or ethnic group. The biggest threat to world peace is the rising of militarism. Militarism means the biggest danger to peace and democracy.

The truth be known the US spends 3-times as much on defense than any other group of nations (the combined EU) and could cut military spending by 2/3rds and still have the strongest military in the world.

I believe that the US has been developing its next generation nuclear weapons over the last decade as well. Of course neither the US or Russia really needs more nuclear weapons albeit the ones we have are getting old.

Militarism does not exist in a vacum it needs people to set it in motion your answer is a cop out which country , religion or ethnic group is most likely to use militarism ?

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"One must never forget that monetary union, which the two of us were the first to propose more than a decade ago is ultimately a political project. It aims to give a new impulse to the historic movement towards union of the European states. Monetary union is a federative project that needs to be accompanied and followed by other steps." — Giscard d'Estaing and Helmut Schmidt

Nearly every country uses militarism. It isn't any ethnic group or so. It are the militarists itself, the Lords of War, the army, minister of defence (or of war) and nationalism. Nationalism and militarism is explosive.

The more militarism the higher is the chance that someone uses it.

Freya has got it right. The biggest threat to peace is extremism, in whatever form it comes in.

China scares the hell out of me. With all of the manufacturing capability, both domestic and military, and the manpower, and their rapid gain in technology, they could easily become a huge world power within the next decade.

Still, the strongest military still belongs to the United States. If you can get the Americans excited about a war, they are a juggernaut, as evidenced by both world wars. However, if its government does not have the support of the American people, any war it wishes to fight is doomed. In addition to that, their technological edge over other countries is still ridiculously vast.

A Chinese-American War would be catastrophic. It would probably develop into world war III, so at this point, China or America is the biggest threat to world peace.

Because after all, an alliance with the strong is never to be trusted.

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"The greatest illusion in life is separation."
-Unknown

"Believe those who are seeking the truth; doubt those who find it."
-Andre Gide

Irans quest for the bomb

Will the world survive a nation that seems so irresponsible and willing to suppress and enslave its own people once it achieves nuclear weapons status and the ability to deliver them regionally? Will they set off a fatal firestorm or just blackmail the world into submission? Will they use the weapon they so desperately seek to destroy their greatest enemies - the USA and Israel? How can the world reason with a nation such as Iran and take a chance that they are willing to use the weapon that they are seeking? Only one nation has ever used a nuclear weapon and that is the United States. The world has been instilled with a understanding that it should never happen again. The problem today is that once the proliferation starts, nations without controls or beliefs that GOD is on their side, the world can be gone in a literal flash.

The world of reason needs to develop metholds of dealing with the unreasonable. One can ask how can we solve such a vexing problem? I do not have the answer but I do know that we do not have an unlimited timeline. One way or another the unreasonable will achieve nuclear status and if the world is not turned into a cinder, it will not be changed for the better.

Iran is not seeking a nuk.bomb unless you have something other than NIE report regarding iran's nuclear program.

Pakistan has Al Qaeda hidden in it's mountains and people who support them while Pakistan already HAS nuclear bombs that can be in their hands if they're not stopped. US is the one that used such weapons till today and iran is the biggest threat

Iran does not consider US as it's biggest enemy, US does. even the most conservservatives now are questioning the 30 years of lack of negotiation with US and say it time to time that they want to have talks with US but it either remains unanswered or US says it will do under the condition of ceasing the nuclear program which they know Iran won't accept.

About Israel, the funny thing is that a big portion of the population of Israel are persian and even they have day named after Iranian ancient king Cyrus the great, who is loved by Iranians too.

Iranians on the other hand are sick and tired of the regim's interferes in Israel-Palestine issues. If Iran achieves a more democratic government that pays attention to people's demands, this won't be an issue anymore because people don't want it.

Nation that is the biggest threat to peace: (tie) U.S./Israel
Generally the biggest threat to peace: (tie) fundamentalism of any kind/the military industrial complex

If judged by contemporary history over the last 50 years no nation even comes close to the number of invasions and military/para-military actions by the US. Under this criteria of "Who commits the most violations of world peace" the US wins hands down.