US vs Iran
How will the Iranians Respond?
One can not compare the size and strength of the United States armed forces to Iran’s. In a conventional war, in a suitable terrain and with enough man-power United States would definitely win. However, as wars in Vietnam (USA), Afghanistan (England, USSR) and elsewhere has shown, wars are seldom fought under ideal conditions (such as fairly flat Iraq). From all indications, the Iranians are aware of this disparity of forces and have been preparing themselves for an eventual confrontation with the US forces. Just from 1992 to 1996 Iran held over 130 military exercises with its ground, air, naval and IRGC forces, and has concentrated on integrating the roles of its various military components, including the Kilo submarines. The manoeuvres have included the rapid deployment of amphibious and covert forces, simulated attacks against oil rigs, submarine warfare, anti-aircraft and anti-ship missile deployment, electronic warfare, chemical weapons defence and the kinds of ship interdictions that would accompany closing the Strait of Hormuz. U.S. Vice Admiral Douglas Katz, former commander of the Mideast Force/U.S. Naval Forces of the U.S. Central Command, told Jane's Military & Training Monitor that "Every exercise the Iranians have conducted for the last two years has been offensive in nature." 
And since 1996, Iranian military exercises have continued unabated, and have become even more sophisticated and larger. For example, the latest military exercise code named “blow of Zulfaghar” resembles a full mobilization. “The state-run television reported that the massive military exercise, aimed at introducing new defensive doctrine, would take place in 14 of Iran's 30 provinces and would last for about five weeks. "Our main objective of this exercise is to adopt new tactics and use new equipment able to cope with possible threats," Brigadier General Kiumars Heydari, spokesman of the exercise, was quoted by the television as saying.” 
“Brigadier-General Mohammad-Reza Ashtiani, the deputy commander of the Iranian Army or Land Branch of the Regular Forces, has specifically accented at a press conference that ‘the war games will take place in the provinces of West Azarbaijan, East Azarbaijan, the Khorasans3, Kurdistan, and the province of Sistan and Baluchestan’4—all of these are Iranian border provinces that would be frontlines in any possible war between Iran and the United States and have been experiencing disturbing episodes of terrorist attacks, kidnappings, violence, and recent instability—which Iran has held the United States, Britain, and Israel responsible for.” 
Dr. Abbas Bakhtiar