Events taking place in a remote stretch of southeast Syrian desert in recent days reveal the current direction of US Middle East strategy.An observable ratcheting up of US and allied air and special forces activity in eastern Syria is under way. This, in turn, appears to derive from a new, hardnosed understanding of the nature of the strategic game in the large, strife-ridden area covering what was once Syria and Iraq.On Thursday, May 18, US aircraft launched strikes on a column of Assad regime vehicles, including tanks and earth-movers, 29 km. from the town of al-Tanf, on the Syrian-Iraqi border. The strikes took place after the vehicles entered an agreed deconfliction zone around the town. US and British special forces are training “vetted partner forces” – i.e., Syrian Sunni Arab rebels – in the town.This was the second occasion in recent weeks that US aircraft have directly engaged Assad’s forces. On the first occasion, the target was the Shayrat Air Base.That raid took place on April 6. It was a clear retaliation for the regime’s use of sarin gas at Khan Sheikhoun on April 4. The Shayrat raid was generally interpreted as a belated attempt to enforce the American redline against further regime use of chemical weapons. As such, it was not widely seen as indicating a more general change of policy.The attack on the column near al-Tanf, by contrast, was not preceded by any unusual regime activity, apart from the approach of the column itself, too close to Western forces. On Monday, the pro-opposition website Syria Direct quoted an unnamed US military spokesman as saying that “if pro-regime forces move further south or east from their current positions, this will be considered a threat.” The website also reported that regime forces are preparing to move toward the Badia area, a stretch of desert to the northeast of al-Tanf.What is the significance of this butting of heads? The battle against the territorial holdings of Islamic State in Iraq and Syria is reaching its final phase. The reconquest of Mosul is almost done. The assault on Raqqa city, the capital of the caliphate, is about to begin. It is set to be a hard and bloody fight, but its eventual outcome is not in question. Islamic State as an entity controlling ground will be destroyed, at which point the movement will revert to its former status as a clandestine terrorist network.As the eclipse of the caliphate draws near, the race is opening up to inherit its former domains.The competitors in this contest are Iran and its various allies and proxies, and forces associated with the West and the Sunni Arab states.The Iranians and their allies want to penetrate Islamic State territory from west to east, with the Iraqi Shi’a militias pushing westward from Tel Afar and Assad regime forces and pro-Assad militias (including Hezbollah) probing east.The regime forces nosing around in al-Tanf are in the process of seeking to seize border areas with both Jordan and Iraq. The US is determined to prevent that.The town of Deir al-Zor and the surrounding oil-rich areas will form an important part of the prize.Pro-Western forces, meanwhile, are pushing north from Jordan and south from the Kurdish-controlled area north of the Islamic State enclave. The forces engaged on this side are the Syrian Democratic Forces, dominated by the Kurdish YPG, and the Maghawir a-Thawra (Commandos of the Revolution, formerly the New Syrian Army) rebels, supported by the US, UK and Jordan, from the south.The outcome of this contest is of strategic significance, despite the remote and arid nature of much of the territory concerned. The Iranians want to create a contiguous line of territory controlled by themselves and their allies, stretching from Iraq into Syria, and thence to the Mediterranean Sea and the border with Israel.Islamic State has formed a buffer against the achievement of this goal. But Islamic State, in the usual manner of Sunni Salafi organizations when they control territory, declined to be satisfied with the stewardship of a small domain. Instead, the Sunni jihadists elected to declare war on the West, using the territory as a base to hold and execute captured Western prisoners, to prepare attacks against Western civilian targets, to administer a regional network of franchise groups, and to attempt genocide against a non-Muslim population, the Yazidis. As a result, the West, unsurprisingly, made it a goal to destroy Islamic State.The question now is who will inherit. The Americans, it appears, have understood that to stand a chance of reestablishing influence and standing in the region, and beginning the process of turning back the Iranian advance, it is necessary to have skin in the game – i.e., to develop reliable proxies and have them control ground in this pivotal area.Only thus can a contiguous line of Iranian control from the Iraq-Iran border to the Mediterranean and Israel be prevented. Only thus will the US be able to prevent an eventual outcome in Syria and in Iraq entirely favorable to the Iranians.Hence, the development by the US Defense Department of the relationships with the YPG and elements among the Jordan-supported Sunni Arab rebels in the south.It is worth also noting that the outcome in eastern Syria is not of primary interest to the Russians.Russia wants to preserve the regime’s existence and to keep its naval investments in Latakia province. Neither of these interests is threatened by events further east.Controlling the east is an Iranian and Assad regime goal only.The outcome of this emergent contest will be of deep interest also to Israeli strategic planners. While some recent analysis has suggested that Israel favors or should favor allowing Islamic State to continue in existence as a quasi-state, it is obvious that this is no longer an option. Syria as a state has largely ceased to exist. The question now, as it is parceled out into zones of influence, is who will gain and who will lose.Alongside the military jockeying on the ground, the diplomatic processes in Astana and Geneva will sputter on. Their eventual outcome, though, will depend on the balance of forces on the ground.Iran wants its contiguous line not least in order to move weaponry and fighters in preparation for, and in the course of, a future war with Israel. Preventing this is an Israeli national security interest par excellence.This emergent US strategy has not yet been officially confirmed. Indeed, Defense Secretary James Mattis was quoted by Agence France-Presse after the al-Tanf strike as denying that the raid heralded any increased role for the US in the Syrian war.The pattern on the ground suggests otherwise. The US administration has defined the Iranians and the Sunni jihadists of Islamic State as its main adversaries in the region. Eastern Syria is an area where the defeat of the latter by pro-Western forces will constitute a setback also for the former. This is a game that is now afoot.Much depends on its outcome.