I read a good article at Safe Haven(The Master Plan for the World and its effect on Resource Stocks) by Claude Maund at following link:
http://www.safehaven.com/showarticle.cfm?id=5986
QUOTE( note:"AXIS" in this articles means USA, UK, Israel)
Some have said that an attack on Iran would bring about World War 3. This suggestion raises two questions. The first is that, in order to have a World War, you have to have an adversary or adversaries with sufficient strength to fight back and have a chance of winning. The other is the question of when a World War become a World War. Just who would fight back in the event of an attack on Iran? The Arab world certainly, but in comparison with the Axis military machine they have little more to fight back with than sticks and stones - bombs and rockets for the most part is all they can muster, while the Axis has the military capacity to vaporize the entire region. Although the Axis predations in central Asia and the Middle East are clearly contrary to the interests of Russia and China, it is doubtful that Russia and China would want to risk the consequences of confronting the Axis directly, even though they have nukes. What is therefore likely to eventuate will be proxy wars, with Russia and China arming Central Asian and Middle Eastern factions to the teeth with advanced weaponry, and this, in combination with relentless and widespread guerrilla warfare waged on Axis forces by resistance fighters in occupied countries, who have the great advantage, militarily speaking, that they believe in what they are fighting for and are willing to die for it to the extent that they are prepared to blow themselves up, would eventually wear down the attenuated Axis forces by attrition, until they pack up and go home. This is already happening to some extent in Iraq. With regard to the question of when a World War becomes a World War, it is illuminating to consider briefly the runup to World War 2. Did this become a World War when Hitler invaded Czechoslovakia, or Austria, or later Poland, France or Russia, or after Pearl Harbor? The answer to this question is the point at which he had aroused opponents with sufficient power collectively to bring him down. So it can probably be said to have become a World War when the Japanese allies of Hitler attacked Pearl Harbor and the United States entered the war. Therefore, when the Axis attacks Iran, what determines whether the situation develops into a World War will be the reaction of other states in the region and across Asia. Iran can be expected to fight back, but will fall and eventually be consumed, but as with Iraq, it will prove to be highly indigestible. Should Russia and China counter with nuclear weapons, or fight a proxy war with the Axis via states in Central Asia and the Middle East, in collaboration with guerrilla fighters in the invaded lands, it will probably be fair to describe it as a World War, because there is a good chance that the Axis will eventually be overcome and forced into retreat.
UNQUOTE
The rest of the article is ok but not relevant as such to current discussion here in this thread.