If the Syrian army enters Lebanon, factions of Iraq’s Popular Mobilisation Forces will cross the border into Syria. If the US launches a ground operation against Iran, Tehran and its regional allies will open new fronts against the Gulf states. If Israel widens its war, Hezbollah will deploy whatever missiles and drones remain in its arsenal.
These scenarios are far from hypothetical; they are threats that Iran has privately conveyed to regional states. And they prove that regional militias allied to Iran are simply proxies that have no independent agency. They are directed by a unified political and security command— the Islamic Revolutionary Guard Corps (IRGC)—with the capability of operating across several fronts at the same time in a coordinated fashion.
The fall of the Assad regime in Syria deprived Iran of its most important land bridge—the route that connected its four principal arms that stretched from Lebanon to Iran via Syria and Iraq. With Syria out of the equation, the so-called "Shiite crescent" strategy was swapped for the "Iranian triangle" that saw the Houthis in Yemen step up in the place of Syria to coordinate with Hezbollah in Lebanon and the Popular Mobilisation Forces (PMF) in Iraq. The two forms (crescent and triangle) are part of a larger strategy that Iran calls 'the axis of resistance', which has largely been effective and has brought the region to the brink of all-out war.
Whatever the form, the 'axis of resistance' strategy is designed to keep war far away from Iranian soil, with regional countries bearing the brunt of kinetic activity. By dispersing war across several theatres, Iran raises the cost of every decision directed against it. An attack on Iran may therefore trigger escalation in the Arabian Gulf, the Strait of Hormuz, the Red Sea, the Bab el-Mandeb Strait, and even as far as the Suez Canal, which could disrupt global trade, supply routes, and energy markets.