Iran’s greatest weakness may have been the static posture it maintained while its external defense in depth was progressively dismantled. However, that comes with a caveat.
(See my article What Would War with Iran Look Like?
Its regional network through Iraq, Syria, and Lebanon had once resembled a modern strategic ribat, extending Iran’s defensive frontier outward and pushing the battlefield away from Iranian territory. When that network weakened, Tehran remained dependent upon fixed facilities, such as established command structures, hardened positions, and long-range retaliation. This allowed its enemies to determine the tempo and sequence of the war.
That does not mean Iran would remain static if foreign troops entered the country. This is where my caveat comes in. Because a ground invasion would likely activate a different form of defense in depth, Iran could fall back through mountains, cities, and tunnels. This, in turn, could help preserve and fortify its internal-security networks, militias, and other irregular or conventional units. The Iranian state appears suppressed under aerial attack for the time being and likely will be for the foreseeable future. The question, and the concern, is whether, if boots were to hit the ground, Iran would shift from a static defense to a mobile defense in depth.
However, the greatest danger to Tehran may not come from American troops advancing directly toward the capital. Rather, it may come from the interaction between external pressure and internal fragmentation. Kurdish forces and other opposition groups could create disturbances along the periphery, forcing the government to divide its forces and attention. However, Iranian command would know better than to venture out en masse to confront a much smaller enemy. The reason for this is that it would expose Iranian forces to U.S. fighters, drones, bombers, and missiles. More consequentially, factions within the Iranian military, bureaucracy, and political establishment could decide that the survival of the present regime no longer coincides with their own survival. In other words, the regime may lose the faith of the very institutions expected to defend it.
Such internal fragmentation could arise by Iran’s own hand or be encouraged through outside assistance. Understand that foreign black-operations personnel may already be operating inside Iran, supported by a much larger clandestine intelligence system working through the country’s institutions, commercial networks, political factions, and administrative structures. Yet the bureaucracy does not end with the institution. Every person encountered represents a bureaucracy of his own. What do I mean by that? Each person has a network of loyalties, ambitions, grievances, fears, obligations, and personal relationships waiting to be understood and, where possible, exploited.
As for the American presence, it is almost phantom-like. It surrounds Iran without presenting a single conventional army for Iran to confront. It appears through air, sea, and cyber, causing sudden destruction against selected targets. Its physical body remains largely outside Iran, while its effects are felt inside the country. It is not merely a phantom, but a deadly phantom: difficult to locate, difficult to engage, and capable of reaching deep into a state that cannot strike it with equal precision.
The strategic purpose of such a presence is not necessarily to conquer Iran from the outside, but to create the conditions under which Iran begins to conquer itself from within. External attacks weaken the connections holding the state together, peripheral factions generate movement, and political uncertainty forces every component of the system to reconsider where its loyalty and survival truly lie. The decisive moment would arrive not when American troops entered Tehran, but when Tehran could no longer be certain which Iranian forces would defend it.
The broader objective is to cripple Iran. The operational apparatus presently employed is largely air, sea, and cyber. A land campaign may eventually follow, but even the possibility of one can serve as a weapon in itself. The threat of American forces entering the country, combined with Kurdish activity and other pressures along the borders, could force Tehran to look in several directions at once while confronting no single conventional invasion force. In other words, Tehran could be forced to defend against deliberately exaggerated or ambiguous armies that might appear.
While Tehran searches for the physical body of the invasion, the United States can continue striking the systems that serve as the regime’s eyes and ears and enable it to defend itself.
Therefore, a land invasion does not have to occur to produce operational effects. Its possibility alone can compel and expose movement, divide attention, and deepen uncertainty. Iran is forced to defend against something that remains largely absent while absorbing punishment from capabilities that are already present. The phantom is not simply the American force itself, but the invasion that Iran must continually anticipate without knowing whether, where, or when it will materialize.