In terms of expansion, the problem for Iran is its mountains. They are as effective a container as they are a defensive bulwark. Supporting an attacking force requires logistics, and pushing supplies through the Zagros in any great numbers is impossible. Unless the Persians can occupy and exploit Iraq, further expansion is impossible. In order to exploit Iraq, Iran needs a high degree of active cooperation from Iraqis. Otherwise, rather than converting Iraq’s wealth into political and military power, the Iranians would succeed only in being bogged down in pacifying the Iraqis.

In order to move west, Iran would require the active cooperation of conquered nations. Any offensive will break down because of the challenges posed by the mountains in moving supplies. This is why the Persians created the type of empire they did. They allowed conquered nations a great deal of autonomy, respected their culture and made certain that these nations benefited from the Persian imperial system. Once they left the Zagros, the Persians could not afford to pacify an empire. They needed the wealth at minimal cost. And this has been the limit on Persian/Iranian power ever since. Recreating a relationship with the inhabitants of the Tigris and Euphrates basin — today’s Iraq — is enormously difficult. Indeed, throughout most of history, the domination of the plains by Iran has been impossible. Other imperial powers — Alexandrian Greece, Rome, the Byzantines, Ottomans, British and Americans — have either seized the plains themselves or used them as a neutral buffer against the Persians.

Underlying the external problems of Iran is a severe internal problem. Mountains allow nations to protect themselves. Completely eradicating a culture is difficult. Therefore, most mountain regions of the world contain large numbers of national and ethnic groups that retain their own characteristics. This is commonplace in all mountainous regions. These groups resist absorption and annihilation. Although a Muslim state with a population that is 55 to 60 percent ethnically Persian, Iran is divided into a large number of ethnic groups. It is also divided between the vastly dominant Shia and the minority Sunnis, who are clustered in three areas of the country — the northeast, the northwest and the southeast. Any foreign power interested in Iran will use these ethnoreligious groups to create allies in Iran to undermine the power of the central government.

Thus, any Persian or Iranian government has as its first and primary strategic interest maintaining the internal integrity of the country against separatist groups. It is inevitable, therefore, for Iran to have a highly centralized government with an extremely strong security apparatus. For many countries, holding together its ethnic groups is important. For Iran it is essential because it has no room to retreat from its current lines and instability could undermine its entire security structure. Therefore, the Iranian central government will always face the problem of internal cohesion and will use its army and security forces for that purpose before any other.

Geopolitical Imperatives

For most countries, the first geographical imperative is to maintain internal cohesion. For Iran, it is to maintain secure borders, then secure the country internally. Without secure borders, Iran would be vulnerable to foreign powers that would continually try to manipulate its internal dynamics, destabilize its ruling regime and then exploit the resulting openings. Iran must first define the container and then control what it contains. Therefore, Iran’s geopolitical imperatives:

Iran's Geopolitical Imperatives

1. Control the Zagros and Elburz mountains. These constitute the Iranian heartland and the buffers against attacks from the west and north.

2. Control the mountains to the east of the Dasht-e Kavir and Dasht-e Lut, from Mashhad to Zahedan to the Makran coast, protecting Iran’s eastern frontiers with Pakistan and Afghanistan. Maintain a line as deep and as far north and west as possible in the Caucasus to limit Turkish and Russian threats. These are the secondary lines.

3. Secure a line on the Shatt al-Arab in order to protect the western coast of Iran on the Persian Gulf.

4. Control the divergent ethnic and religious elements in this box.

5. Protect the frontiers against potential threats, particularly major powers from outside the region.

Iran has achieved four of the five basic goals. It has created secure frontiers and is in control of the population inside the country. The greatest threat against Iran is the one it has faced since Alexander the Great — that posed by major powers outside the region. Historically, before deep-water navigation, Iran was the direct path to India for any Western power. In modern times, the Zagros remain the eastern anchor of Turkish power. Northern Iran blocks Russian expansion. And, of course, Iranian oil reserves make Iran attractive to contemporary great powers.

There are two traditional paths into Iran. The northeastern region is vulnerable to Central Asian powers while the western approach is the most-often used (or attempted). A direct assault through the Zagros Mountains is not feasible, as Saddam Hussein discovered in 1980. However, manipulating the ethnic groups inside Iran is possible. The British, for example, based in Iraq, were able to manipulate internal political divisions in Iran, as did the Soviets, to the point that Iran virtually lost its national sovereignty during World War II.

The greatest threat to Iran in recent centuries has been a foreign power dominating Iraq — Ottoman or British — and extending its power eastward not through main force but through subversion and political manipulation. The view of the contemporary Iranian government toward the United States is that, during the 1950s, it assumed Britain’s role of using its position in Iraq to manipulate Iranian politics and elevate the shah to power.

The 1980-1988 war between Iran and Iraq was a terrific collision of two states, causing several million casualties on both sides. It also demonstrated two realities. The first is that a determined, well-funded, no-holds-barred assault from Mesopotamia against the Zagros Mountains will fail (albeit at an atrocious cost to the defender). The second is that, in the nation-state era, with fixed borders and standing armies, the logistical challenges posed by the Zagros make a major attack from Iran into Iraq equally impossible. There is a stalemate on that front. Nevertheless, from the Iranian point of view, the primary danger of Iraq is not direct attack but subversion. It is not only Iraq that worries them. Historically, Iranians also have been concerned about Russian manipulation and manipulation by the British and Russians through Afghanistan.

The Current Situation

For the Iranians, the current situation has posed a dangerous scenario similar to what they faced from the British early in the 20th century. The United States has occupied, or at least placed substantial forces, to the east and the west of Iran, in Afghanistan and Iraq. Iran is not concerned about these troops invading Iran. That is not a military possibility. Iran’s concern is that the United States will use these positions as platforms to foment ethnic dissent in Iran.

Indeed, the United States has tried to do this in several regions. In the southeast, in Balochistan, the Americans have supported separatist movements. It has also done this among the Arabs of Khuzestan, at the northern end of the Persian Gulf. And it has tried to manipulate the Kurds in northwestern Iran. (There is some evidence to suggest that the United States has used Azerbaijan as a launchpad to foment dissent among the Iranian Azeris in the northwestern part of the country.)

The Iranian counter to all this has several dimensions:

1. Maintain an extremely powerful and repressive security capability to counter these moves. In particular, focus on deflecting any intrusions in the Khuzestan region, which is not only the most physically vulnerable part of Iran but also where much of Iran’s oil reserves are located. This explains clashes such as the seizure of British sailors and constant reports of U.S. special operations teams in the region.

2. Manipulate ethnic and religious tensions in Iraq and Afghanistan to undermine the American positions there and divert American attention to defensive rather than offensive goals.

3. Maintain a military force capable of protecting the surrounding mountains so that major American forces cannot penetrate.

4. Move to create a nuclear force, very publicly, in order to deter attack in the long run and to give Iran a bargaining chip for negotiations in the short term.

The heart of Iranian strategy is as it has always been, to use the mountains as a fortress. So long as it is anchored in those mountains, it cannot be invaded. Alexander succeeded and the Ottomans had limited success (little more than breaching the Zagros), but even the Romans and British did not go so far as to try to use main force in the region. Invading and occupying Iran is not an option.

For Iran, its ultimate problem is internal tensions. But even these are under control, primarily because of Iran’s security system. Ever since the founding of the Persian Empire, the one thing that Iranians have been superb at is creating systems that both benefit other ethnic groups and punish them if they stray. That same mindset functions in Iran today in the powerful Ministry of Intelligence and Security and the elite Islamic Revolutionary Guards Corps (IRGC). (The Iranian military is configured mainly as an infantry force, with the regular army and IRGC ground forces together totaling about 450,000 troops, larger than all other service branches combined.)