An Occupation of Iran? Crunching the Numbers

Amid the Trump administration's tearing up of the 2015 deal the U.S. made with Iran regarding its nuclear program, the escalation of tensions in the region, the dispatch of substantial U.S. forces to its region, and the recent downing of a U.S. drone which, it is reported, led to the order of a retaliatory air strike rescinded mere minutes before it went through, there has been more than the usual consideration of full-blown war between the two countries--with one possible U.S. objective being the regime change in Iran long coveted by the neoconservatives, who have been in the ascendant again in Washington.

All of this, of course, evoked the memory of the attempt to do so in Iraq in 2003, which saw a highly successful conventional campaign--and disastrous aftermath. Rather than the brisk, easy transition from the Baathist regime to a more congenial successor, what resulted was a complex of wars that, in their metastasizing into the war with the ISIS organization, spilled across Iraqi borders in catastrophic fashion (and in Syria led the U.S. to perhaps its most dangerous confrontation with Russia in over a half century). And that memory has, in turn, raised the question of what would be required for an occupation of Iran were the administration to carry its action that far.

One approach to the problem has been to extrapolate from the requirements of the occupation of Iraq to those that similar action against Iran might require. One estimate espoused by then-Army Chief of Staff General Eric Shinseki was that hundreds of thousands--perhaps 800,000 troops--would be needed for occupation duty. Secretary of Defense Donald Rumsfeld insisted that a force a fraction that size (100,000) would be sufficient. As events quickly and predictably showed, they were not, and one could (conservatively but not unreasonably) take that 800,000 figure as a baseline.

Iran has over three times' Iraq's population (82 million to the 25 million or so Iraq had then), and almost four times' its territory (636,000 square miles to Iraq's 169,000), one could plausibly picture three to four times' the number of troops being necessary. On this basis scholar of Middle Eastern history Juan Cole tripled the 800,000 figure for 2.4 million in his own analysis, but one could just as easily speak of 2-3 million.

The need for up to 3 million troops to occupy Iran may, even in light of the Iraqi precedent, seem unduly pessimistic. After all, 3 million troops was what the U.S. had in Europe on V-E Day, and just over half those (1.6 million) in Germany, and even that figure dropped rapidly afterward.

And surely occupying Iran is a smaller job than occupying Germany?

The reality, however, is that Iran is a quarter more populous than Germany was in 1945, over four times as big as Germany was in area. Indeed, it is an eighth larger than Germany, the Benelux countries, Austria, France and Italy combined (a collective 560,000 square miles or so).

It should also not be forgotten that that occupation was a joint effort with the other Allies, not least Britain, France and the Soviet Union, with smaller areas assigned other nations like Belgium, Norway and Poland, the commitment discussed here a mere fraction of what was required. Where American occupation of Germany specifically is concerned, it should be remembered that the U.S. zone in western Germany amounted to a rough quarter of Germany, some 33,000 square miles and 16 million people--a twentieth of the territory and a fifth of the population of Iran today--and at the time this demanded some three hundred thousand troops a year after the end of the war.

Worth considering, too, is the occupation of post-war Japan the U.S. carried out more single-handedly, with nearly a half million troops at the outset when the Ryukus are included.

Iran is more than four times as large as Japan (636,000 to 145,000 square miles); and its population substantially larger than Japan's was at the time (81 million to 70 million or so).

The reader should also note that Iran is substantially more urbanized than Western Europe or Japan was at the time (nearly three-quarters of its people living in cities, compared with a third or so of Japan's in that period)--a fact which makes territorial occupation more rather than less manpower-intensive. One may point out, too, that in contrast with the situation in a Europe firmly under Allied control in 1945, or insular Japan, Iran has very long, very mountainous borders with populations in Iraq, Afghanistan and Pakistan which might view the highly likely emergence of violent opposition to a U.S. occupation with sympathy. This would enlarge the problem of controlling the country, and perhaps, lead U.S. operations to extend beyond it in the event of trouble (just as the attempt to occupy Afghanistan drew the U.S. into involvement in Pakistan).

Also significant is the fact that armies have changed, especially high-tech mechanized armies like those of the U.S., whose proportion of "tail" to "tooth" has risen enormously. In the World War II period some 65 percent of troops were combat personnel, but the figure was down to a quarter by the early twentieth century. One could argue for an even sharper drop in the "foxhole strength" a large unit could muster--troops who would be available to, for instance, patrol on the street rather than keep the gear running, or the flow of supplies continuing to come in. This raises the necessary ratio of troops-to-occupied yet again.

Given these precedents with regard to territory, population, urbanization and borders, and the tasking of any given quantity of military manpower in the current high-tech, high-tail era, a total figure comparable to the U.S. force in Western Europe, or a multiple of the force inserted into Japan, does not seem at all outside the bounds of the plausible.

Of course, this is far beyond the capacity of American forces as presently constituted. Consider the active-duty U.S. armed forces. These come to some 1.3 million personnel. However, half of that is Air Force and Navy--and the other half Army and Marines. Moreover, of the 660,000 or so Army and Marines (480,000 Army, 180,000 Marines) not all are ground troops trained, armed and organized into usable formations.

The two services have some 13 divisions between them--on average, 15,000 troops each. This comes to about 200,000 troops that could actually be put on the ground--a third of the 660,000 figure, and the rest a vast organization for recruitment, training, administration and support in logistical and other ways required to keep those 200,000 in the field, especially in a faraway country. Additionally, it would be out of the question for the entire force to be deployed to one contingency, at once. The U.S. has military commitments all over the world; and in any event, units are rotated in and out of operational duty. (They need rest; they need retraining and reconstitution.) This is the case even in world wars. As a result, rather less than the whole would be available for a given task.

Of course, there are reserves. The Army and Marine Reserves together have some 240,000 personnel (200,000 Army, 40,000 Marines), while the Army National Guard can supply 340,000 more. However, one again has to think in terms of actual, usable ground units. The Army Reserve has 8 divisions, the Marine Reserve one, the Army National Guard 8 more divisions than that--a maximum of 17 divisions in all, and plausibly some 250,000 personnel, whose actual use would be subject to the same constraints as the active-duty troops.

Recent U.S. experience is telling. Even with the biggest mobilization of reservists since the Korean War swelling their ranks (150,000 National Guard and Reservists, providing up to a quarter of the force rotating through Iraq), keeping 200,000 troops in Iraq and Afghanistan--equaling just a quarter of nominal Army and Marine strength at the time--was a considerable strain.

The result is that even a complete mobilization of the Reserve and National Guard (a time-consuming process that will raise the political difficulty of action) gives the U.S. under a half million deployable combat troops, and to go by the Iraq precedent, just 300,000-400,000 available for all operational contingencies.

It is somewhere between a fifth and a tenth of the 2-3 million personnel figure.

Now think about what it would take to close that gap. It would not be a simple addition of 2-3 million more troops, but 2-3 million in deployable combat units. Assuming the ratios of nominal service strength and combat strength remain the same, this will mean an enlargement of the Army (the more logical locus of the expansion, given the Marines' more specialized nature as an amphibious assault/rapid reaction force) to 6 million, 8 million, or even more. It is scarcely conceivable that such a body of ground troops could be supported abroad without a commensurate expansion of the Air Force and Navy, and especially their airlift and sealift capacities, meaning millions more personnel in those forces. In the end one might imagine something like that all-services' wartime peak, 12 million under arms in all.

The U.S. population is about two-and-a-half times larger today than it was during in World War II (330 million to 130 million then). Still, raising such a force would mean a fairly comprehensive draft, as some of the more astute observers have pointed out.

Daunting as all this sounds, it still overlooks a key issue here, which is that one ordinarily has to defeat a country's armed forces before they can occupy their territory. Given recent U.S. experience--above all, with Iraq--this may seem a simple matter. Still, Iraq proved an exceptionally "convenient" opponent. It had a long border with Saudi Arabia and Kuwait, permitting the U.S. and allied forces wide leeway in their approach to the country, the more so given the open desert of the south. The Iraqi armed forces had already been badly mauled in the 1991 Gulf War, and substantially denied a chance to recover by international sanctions (with its air force and air defenses further degraded by low-grade air war). When war broke out, Iraq waged a defensive conventional campaign of a kind that left its forces as vulnerable as they could conceivably be to American strengths. And of course, the 2003 conflict saw Iraq totally on its own, with Russia, China and other actors limiting themselves to political opposition.

By contrast Iran's borders afford no such convenient entry points or staging areas. With four decades to adapt since the loss of American and British sponsorship, and three decades to recover from their last major war, Iran's armed forces are in a far less battered condition--and for all their undeniable limitations with regard to equipment and other matters, far more numerous (with the regular military, Revolutionary Guard and Basij paramilitaries plausibly raising 2 million or more). Iran may be less passive than Iraq in regard to a build-up nearby, using its far less likely to fight back along the rigidly conventional terms so implausible given the undeniable disparity in military power (with the prospect of unconventional Iranian naval tactics being used to sink American warships oft-noted). And of course the country will be nowhere near so isolated--with the possibility of Russian intervention impossible to leave out of any such calculations. Indeed, a U.S. attack on Iran may be less tolerable to Moscow than regime change in Syria because of the country's bordering ex-Soviet states Azerbaijan, Turkmenistan and Armenia, as well as its size and energy reserves; while the logistics of Russian intervention would be easier. (Russian aircraft need only fly over the Caspian, while enjoying quite direct access to Iranian airspace through bordering states.) While a Chinese response seems far less likely to take the form of direct military intervention, the country's objections to such action are likely to count for much more in 2019 than they did in 2003.

In short, any conflict against Iran, not simply including a full-blown national occupation, but any military action whatsoever, is quite a different thing from the question of action against Iraq in 2003--which itself proved a far, far different thing from what Donald Rumsfeld and company promised.