For the past three years, the Middle East’s strategic landscape has been changing at a rapid pace. Two recent events are noteworthy. Last month, the Iran-backed Shiite Houthis took over Yemen’s capital, Sanaa. The Houthis have now reached Bab Al-Mandab, the strait at the southern tip of the Arabian Peninsula where more than three million barrels of oil pass daily. Meanwhile, despite the airstrikes campaign against it, the jihadist group the Islamic State in Iraq and Syria (ISIS) has expanded its footprint by advancing into several Kurdish towns on the Turkish border.

These two developments affect the strategies of the region’s four key powers—Saudia Arabia, Turkey, Iran, and Israel.

1. Saudi Arabia is now surrounded, in the north and the south, by powers aligned with Iran, as various Shiite militias control Iraq and the Houthis seize Yemen.
2. Turkey, which for the past year has observed from a distance the war in Syria and the perilous expansion of ISIS in the eastern Mediterranean, is now compelled to confront that peril.
3. Iran faces a different situation. In the past two years, its proxies in Iraq, Syria, Lebanon, and Yemen have achieved significant gains. Now Iran is obliged to increase support for them. If these groups suffer major setbacks, Iran will be perceived as an unreliable strategic backer; crucially, it will lose important tools in the unfolding battle over the shape of the new Middle East.
4. Israel, emerging from this summer’s Gaza war with mixed results, is gradually coming to terms with the reality that, despite its unrivalled military power and major intelligence reach, it can no longer mould its immediate neighborhood, let alone developments across the region.

The four players will adopt similar tactics. They will use selective force—notably, airstrikes and special operational units—to weaken the groups they deem perilous (whether ISIS, the Houthis, Hamas, or other militant groups). They will avoid ground battles. Through financial incentives, they will divide these militant groups, buy off some factions, and turn adversaries against one another.

These developments also create opportunities for the four powers. Whether in Syria, Lebanon, Iraq, or Yemen, the regional powers will attempt to weaken central authority in each in the fronts where their interests are concentrated. Non-state actors (almost all of which are pawns of the regional powers) will become more influential than official governments. Iraq and Syria have already been subjected to some sort of Lebanonization, as different militias and political blocs have spheres of influence that match, if not exceed, those of the central government. As has been the case in Lebanon for over two decades, in Syria, Iraq and Yemen a balance of power among non-state actors will emerge as the sole guarantee of avoiding total state-collapse.

The balance will be fragile. Given the war in Syria, intense sectarianism in Iraq and Lebanon, the war on ISIS, and the existence of over two millions refugees who threaten the delicate demographics of Lebanon and Jordan, the eastern Mediterranean is prone to more geopolitical shocks. Two are particularly dangerous.

Turkey’s intervention against ISIS takes place in an area heavily populated by Kurds. If that intervention (even without ground forces) results in significant civilian casualties—or in the case of a ground invasion, leads to a quasi-Turkish occupation of some ethnically Kurdish towns—this could instigate Kurdish antagonism against Turkey. In turn, violence could spread to eastern Turkey, a region with sizable Kurdish and Alawite communities. In such a scenario, Turkey’s intervention might amplify, rather than contain, the chaos at its doorstep.

The second potential shock concerns Israel and Iran. Despite a few surgical operations in the Golan Heights, Israel has been cautious not to directly attack Iranian assets in Lebanon or Syria. Iran, despite being Hezbollah’s principal supporter, has so far respected Israel’s red lines, especially in terms of the arms or logistical support it provides to Hamas. But if the equilibrium shifts, the resulting chaos could lead both Israel and Iran to miscalculate each other’s red lines. One mistake could flare up another Israel-Hezbollah war.

In Yemen, the fragilities are stark. Yemen is much poorer than Syria, Iraq, and Lebanon. It lacks Jordan’s open financial markets and sophisticated infrastructure; its real estate market is depressed. Yemeni tribes and warlords vying for influence have few economic incentives to protect. Relative poverty denies Yemen one of the key safety valves that has, so far, has protected several countries in the eastern Mediterranean from destruction.

Yemen, however, is deeply linked to organized crime. Several criminal groups have benefited from providing logistical support to pirates operating in the Horn of Africa as well as drug syndicates, some of which are connected to the jihadist group Shabab in Somalia, and to human traffickers focusing on East Africa. These groups thrive amid fluidity and violence. They have already been stoking fire between the Houthis and some of Yemen’s large tribes.

The confrontation in Yemen provides Iran with a valuable opportunity to destabilize (or at least distract) its strategic opponent, Saudi Arabia. The capital, Sanaa, is few hundred kilometres from the Saudi border. Many of Saudi’s leading merchant families have strong tribal connections to Yemen, and the country has traditionally fallen in Saudi’s sphere of influence. The kingdom will not accept the Houthis’ control of Sanaa. Iran’s hope is that Yemen’s complicated situation will prove to be Saudi’s Vietnam war.

The Saudi national security establishment is aware of the risks and yet is compelled to intervene in Yemen. Saudi will deploy the resources of its alliance with the United Arab Emirates, Kuwait, and Bahrain against Iranian influence in Yemen. Because of Yemen’s vulnerabilities, the confrontations will persist for months at least. It will likely spread beyond the country. Some of the Houthi groups, and other proxies, will extend their operations to Saudi and its allies. Yemen’s crisis could descent the Gulf into becoming another fluid front in the explosive Middle East.

Tarek Osman is the author of the international bestseller Egypt on the Brink.