Defending Diego Garcia

Defending the US facility on Diego Garcia never used to present much of a challenge.

The base was far out of range of regional actors who might want to threaten it, so there was no need for the surveillance and air defense resources needed to protect US bases within the Middle East region, such as are needed at Ain al-Assad in Iraq, at Al Tanf base on the Syrian-Jordanian border and elsewhere - bases which have been regularly attacked. Nor was there a need to construct hardened aircraft shelters. For US defense planners, this presented a considerable saving in resources.

Small boat intruders were kept away by the sheer distance from the nearest dry land. A small force of British Royal Marines appears from nowhere to intercept boats trying to enter the 250,000 square mile Marine Protected Area within which Diego Garcia sits, sometimes reinforced by the River Class Offshore Patrol Vessels HMS Spey (P234) or HMS Tamar (P233).

Just as negotiations between the United Kingdom and Mauritius over the future of Diego Garcia appear to be coming to a conclusion, this situation appears to be changing - highlighting the geopolitical perils of predicting requirements and the future 99 years ahead when coming to international agreements of this nature.

As tensions between Iran and the United States have ratcheted up in recent months, it has become apparent that Iran has now developed missile and drone systems that can pose a direct threat to the base on Diego Garcia. Previously Iran appears to have observed a moratorium on developing long-range missiles. But with UN Security Council Resolution 2231 due to expire on October 18, Iran could well unveil longer range versions of the Khorramshahr missile developed in secret, which could have Diego Garcia in range if launched from the Chah Bahar area - whose air base was visited by VIPS escorted by Brigadier Hamid Vahedi, commander of the Iranian Air Force, on April 6.

Other long range systems have already been tested. Iran’s Shahed-129 and Fotros attack drones can already manage the 2,500 miles to Diego Garcia. A large fleet of medium range missiles and drones could also be fired at Diego Garcia from the IRGC Navy’s converted oil tankers Shahid Mahdavi (C110-3) and Shahid Bagheri (C110-4). Moreover, as well as having the capability, Iran has also boasted of its intention to threaten Diego Garcia.

Hence it is no surprise that to watch over the B2-Sprint and KC-135 long-range strike capability deployed in recent weeks to Diego Garcia, the US Navy has deployed Arleigh Burke Class destroyer USS Wayne E Meyer (DDG108) to the area to bolster local air defenses. With Diego Garcia now also replenishing the USS Carl Vinson Carrier Strike Group, such precautions are necessary, and may become even more so if the current ongoing strikes on the Houthis in Yemen conflagrate into wider conflict.

But for the long-term, keeping an Arleigh Burke on station is an expensive way of providing air defense, particularly when such naval air defense resources are now needed for the first time and are being deployed in sea areas adjacent to Mexico. It might be cheaper and more sustainable if a local air defense infrastructure for Diego Garcia were to be put in place.

This could entail positioning and air defense and surveillance assets up range from Diego Garcia on other islands in the Chagos Archipelago, the best candidate being Peros Banhos, which was the last island in the archipelago to remain occupied before the local population was evacuated, and where traces of some infrastructure remain.

Until the draft of the treaty between the United Kingdom and Mauritius is released, it is unclear if such a deployment would be permitted. Nor is it clear what arrangements more generally are to be put in place to ensure that the defense in depth for Diego Garcia currently provided by the British-patrolled Marine Protection Area can be continued.