"Which Path to Persia?" 
was written in 2009 by the Brookings Institute as a blueprint for confronting Iran.

..........the occupation of Iran even more, to levels that realistically only could be met by a major, rapid expansion of the U.s. armed forces, for which the American people appear to have little interest. 

Political requirements Because the military requirements of the occupation and reconstruction of Iran are so daunting, and the likelihood of international support in this scenario appears so low, the first and most important requirement would be the overwhelming political support of the American people for an invasion. simply put, compared to U.s. involvement

in Iraq, the invasion and reconstruction of Iran is likely to be a more taxing task even assuming that the United states avoids repeating the mistakes of Iraq and there will be even less foreign assistance to accomplish it. 

This means that the president would have to have such strong and enduring support from the American people that he would be able to conduct the invasion and occupation of Iran employing essentially only American resources and in the face of widespread international animosity. 

He might need to mobilize fully the National Guard as well as the army, Marine, and possibly Navy reserves and keep them in uniform for months or even years if there is considerable Iranian resistance, as there may well be. in worst-case scenarios, the president might even need to ask the American people to accept some form of limited conscription. 

If the occupation of Iran were to go badly, there might be considerable American casualties for long periods of time—possibly even more than in Iraq at its worst because of the more difficult terrain, the likely greater hostility of the populace, and the greater proficiency in guerrilla warfare of the Iranian military. if the president can secure this kind of support, an invasion of Iran is a viable option. Without such support, the invasion and occupation of Iran

The following are the advantages and disadvantages of the Invasion approach.

advantages: The most important and obvious advantage of mounting an invasion of Iran is that it would “solve” all of Washington’s current problems with Tehran. 

Iran’s nuclear program would be obliterated. The regime that supported so many terrorist, insurgent, and revolutionary groups that sought to harm the United states and/or its regional allies would be gone. shillalah, Hamas, the Palestinian Islamic Jihad, and the like would have lost one of their most important backers. and Washington would no longer have to worry about how to deal with a regime it considers both threatening and maddeningly opaque.

Moreover, a policy focused entirely on mounting an invasion of Iran would be

implemented entirely under American control. Washington might find itself in a

position where it would not need to worry about convincing reluctant allies, since

there would be no expectation that they

could be convinced nor any expectation

that they would help. Furthermore, Washington would not need to persuade the Iranian leadership (or even Iranian dissidents) to cooperate with the United states, it could force them to do so, or simply get rid of them and bring in a whole new group.

Finally, it would mean employing the most powerful, most skillful, and most decisive tool in the U.s. strategic toolkit—the American armed forces—to “fix” the Iran problem. Neither American covert operatives nor diplomats nor aid mavens have had a track record as good as U.s. soldiers, sailors, airmen, and Marines over the years.

Disadvantages:

an invasion of Iran would be extremely costly in a whole variety of ways. Iran is

arguably a more complex, convoluted, and conflict-ridden society than either Iraq or Afghanistan. But like Iraq, it would be too important to be cast aside after deposing the regime and razing all its nuclear and terrorist-support facilities. The invasion it- self would be large and costly, but the effort needed to occupy, secure, and then build a new Iranian state—one capable of governing the country effectively without falling into chaos or inciting new anti-Americanism—would be far more so. 

Even if Washington has learned all of the lessons of Iraq and Afghanistan and handles an invasion of Iran in a much better fashion, this option would cost tens—if not hundreds—of billions of dollars a year for five to ten years. 

It would require the commitment of the better part of U.s. ground forces for several years, and could necessitate a much greater commitment and expansion of American ground forces than at any time since the second World War. it might even require the institution of partial conscription for some period of time and would divert badly needed assets away from both Iraq and Afghanistan.

Another inevitable cost would be in American lives lost (not to mention Iranian civilian deaths). hundreds or possibly thou- sands of American military personnel

would die in the invasion itself. Thereafter, casualty levels would depend dramatically on both the extent of Iranian resistance and the competence of the American security effort. The remarkable success of American forces in Iraq since 2007 demonstrates that the right numbers of troops

employing the right tactics in pursuit of the right strategy can secure a country at much lower cost in blood than inadequate numbers of troops improperly employed. 

Prior to the surge—and during its heated early months when U.s. troops were fighting to regain control of Iraq streets American military deaths were running at 70 to 80 a month. once that fight had been won, they fell to roughly 5 to 15 a month. This suggests that U.s. casualties during the occupation and reconstruction of Iran could vary enormously; however, only in the best-case scenario—where the securing of Iran is as smooth as the NATO securing of Bosnia should policymakers expect minimal casualties. 

In more plausible but still favorable scenarios where Iranian resistance approximates Iraqi levels of violence after the surge, the United states should still expect a dozen soldiers and Marines to be killed each month, on average, for several years. 

In worst-case scenarios, in which the United states mishandles operations in Iran as badly as it did initially in Iraq, those numbers could run into the hundreds each month, or worse.

Washington would have to expect Tehran to retaliate against American targets outside of Iran. Iran has a more formidable ballistic missile arsenal than Saddam had in 1991 and a far more extensive and capable network to mount terrorist attacks beyond its borders. Whether the Iranians could pull off a catastrophic attack along the lines of 9/11—would depend on how much time they had to prepare for such an operation and how well developed their contingency plans were at the time. 

Washington has long believed that Tehran maintains extensive contingency plans for all manner of terrorist attacks against American targets for just such an eventuality, and may even have practiced them at various times. even if such attacks ended with the fall of the regime, since an invasion might take as much as six months from the time the first U.s. Navy warships began to clear the strait of Hormuz to the removal of the clerical regime, the United states would have to prepare to prevent such attacks and live with the failure to do so for at least this time period.......Read More