Maritime security remains a critical concern in the narrow strait of Bab al-Mandab, the so-called "Gate of Tears" that connects the Gulf of Aden and Arabian Sea to the Mediterranean via the Red Sea and Suez canal.
Flanked by Yemen and Djibouti, the strait is 29km wide at its narrowest point, limiting tanker traffic to two 3.2km-wide channels for inbound and outbound shipments, according to the US Energy Information Administration (USEIA).
An estimated 6.2 million barrels per day of crude oil and petroleum products flowed through Bab al-Mandab in 2018, USEIA said, and in 2017, about 9% of total seaborne-traded petroleum flowed through it, destined for various markets.
In addition to oil, Maritime Executive magazine noted in a June 14, 2020 report, local and international merchant shipping, military vessels, fishing trawlers and cruise ships pass through Bab al-Mandab.
Though it is in the interests of most nations to keep maritime traffic and trade flowing, rogue actors such as the Iran-backed Houthis in Yemen pose a threat to the strait's security, and piracy also has been a recurring concern.
Bab al-Mandab and the Gulf of Aden, vital routes for the regional and global flow of trade and commerce, remain under threat from the Houthis, which Iran continues to arm through its Islamic Revolutionary Guard Corps (IRGC).
In a January 25 report to the UN Security Council, a panel of experts on Yemen documented three routes used by the IRGC to smuggle weapons to the Houthis, one of which passes through Bab al-Mandab.
Regional and international forces also have been preparing for possible scenarios in which Iran directly attempts to impede the freedom of navigation of oil and commercial tankers in the region, including in Bab al-Mandab.
There would be far-reaching consequences in the event of such a closure.
In an August 27, 2019 report, USEIA noted that a closure of Bab al-Mandab could keep tankers originating in the Arabian Gulf from transiting the Suez canal or reaching the Suez-Mediterranean (Sumed) pipeline.
The pipeline extends from the Gulf of Aqaba to the Egyptian port of Alexandria.
A closure of Bab al-Mandab would force tankers to take a much longer and costlier route around the southern tip of Africa.
'Guarding the gate'
The world cannot afford to have the busy waterway crumble into lawlessness and cripple a trade system and regional economy, the Maritime Executive report said, pointing out that "somebody needs to guard the gates".
"Securing this chokepoint is vital to the US and its allies, but they are not the only ones seeking to gain the upper hand in this turbulent patch of ocean," it said.
"One of the more plausible naval coalitions that could achieve control of the Bab al-Mandab would be the US-led Combined Maritime Forces," it added.
The Bahrain-based CMF is a 34-nation maritime partnership that promotes security, stability and prosperity across approximately 5.1 million square kilometres of international waters.
In addition to Bab al-Mandab, these waters include the Arabian Gulf, the Strait of Hormuz, the Gulf of Oman, the Gulf of Aden and the Red Sea.
The partnership's forces train together in regional waters and work to protect and defend shipping while it is transiting through global commerce lanes.
They uphold the International Rules-Based Order by countering illicit non-state actors on the high seas and promoting security, stability and prosperity.
The CMF already covers Bab al-Mandab, Maritime Executive noted, but traditionally has been more focused on the Arabian Gulf and Gulf of Aden.
"Nevertheless, the CMF has the flexibility, skills and credibility to take on a greater role in the Bab al-Mandab," it said, suggesting that "an increased – and increasingly visible – presence by the US and its partners is warranted".
A stronger US-led presence could leverage existing partnerships and work with new partners, it suggested, noting that "equally overt diplomatic and economic engagement" also would help to build regional trust.
US Naval Forces Central Command (NAVCENT) also works to secure navigation through Bab al-Mandab in order to ensure the smooth flow of commercial activity in regional waters.
This work has included removing sea mines planted by Iran and the Houthis.
The International Maritime Security Construct and its Coalition Task Force Sentinel is an additional mechanism to secure navigation in Bab al-Mandab, the Strait of Hormuz, the Sea of Oman and the Arabian Gulf.
Formed in September 2019, following a spate of Iranian attacks on oil tankers and merchant ships, it comprises the United States, the United Kingdom, the United Arab Emirates, Bahrain, Saudi Arabia, Lithuania, Australia and Albania.
The international alliance is designed to protect merchant ships and ensure freedom of navigation and international trade.