While Trump’s decision to bomb a Syrian airfield in response to use of chemical weapons by the Syrian government got the lion’s share of the press attention about American involvement in Syria (probably because of the contrast with Obama’s preference for diplomacy despite his “red line” threat), the more important strategic operations have not been discussed as fully. Building upon the successful establishment of two airfields last year, the US has expanded or established bases at crucial locations and begun to attack key targets in the northern part of Syria that show an excellent understanding of the topography and logistics of the region. These developments may be the linchpin in choking off traffic and crippling supply and movement of ISIL, and should contribute to the long-term goal of securing Hasakah and Raqqah provinces. What is interesting in all of this, perhaps due to the historical expertise of National Security Adviser H.R. McMaster, is that this logistical focus mimics the attack routes that were vital to invasions of the area from Alexander the Great down to Julian the Apostate.
The Euphrates River as an ancient supply highway
In the era of Alexander the Great, supply and communication were important constraints on military action; the logistics of his march through Syria are extremely well described by Donald Engels. Essentially, because of the lack of water sources in surrounding areas, the rough Taurus Mountains to the north and Arabian Desert to the south, and the provisions and easy transport supplied by it, the Euphrates River was a common “highway” for military movement in antiquity. Controlling and utilizing it was essential to control of the trade and military actions between the Mediterranean coast and Mesopotamia. In his defense against Alexander, Darius III kept his army on the Euphrates, and Alexander surprised him by crossing northern Mesopotamia to follow the Tigris River (near Mosul, which ISIL also recognized as vital) instead. However, almost every major invasion of the area from the west has gone through what is now southeastern Turkey to reach the headwaters of the Euphrates, including those of Trajan, Septimius Severus, and Julian the Apostate. Crassus reaped the gruesome rewards of avoiding the Taurus/Euphrates route.
The Euphrates valley was important not only as a military route, but also as a source of agricultural income and a crucial portion of the early Silk Road. Therefore, the nation that controlled the northern Euphrates valley could finance their military through control of trade and taxation (which Zenobia’s husband used to assert his own quasi-independence from a city that ISIL has ironically destroyed), a fact that has changed only in the economic transition from agricultural production to petroleum extraction. Now, ISIL not only taxes and sells oil to support its endeavors, but it knew from the outset to seize strategic locations on the route and even wanted to use the Euphrates river as its logo!
The mountains north of the Euphrates
The famous historian and general, Xenophon, was part of an army that followed the Euphrates down to a fateful battle at Cunaxa, and his retreat through the Taurus Mountains and ancient Armenia involved encounters with natives who were extremely capable in skirmishing on mountainous terrain. Both Xenophon and Mark Antony learned how difficult this route was, and the successful Kurdish defense of the Sinjar mountains and victories in the mountains of northeastern Syria using small arms and mobile forces while conceding villages is reminiscent of these ancient raiding methods. Though bombing obviously differs in technology and methods from ancient infantry, it also involves avoiding direct battle in order to destroy resources and harass enemy armies in motion, and so the American strategies based on assaults from the Rmeilan and Incirlik airfields over the past year have used the same attrition tactics to wear down ISIL strongholds.
What comes next?
If ancient campaigns can tell us anything, it may be that the US is transitioning from bombing from afar to more direct assaults on the cities, roads, and resources of ISIL along the northern Euphrates. The US still holds bases in northwestern Syria, defending the western flank of Kurdish-controlled territory and providing a buffer to Turkey (which, along with Turkish efforts to stop individual penetration of the border, should mitigate ISIL recruitment and international travel). Now that it has augmented this by creating bases that choke off routes to the headwaters of the Euphrates and allow closer engagement with ISIL since January, the US seems to be poised to contain ISIL attacks with greater alacrity and support Kurdish ground assaults on the ISIL capital of Raqqa. The escalation may be as support in the race to Raqqa and to take advantage of victories in eastern half of the campaign in Mosul, and comparison to the campaigns cited above would indicate that the US and Kurds are moving much slower than ancient campaigns, but using the same routes, attacking targets in similar ways, and with the same respect for topography and logistics.