I. Introduction

Recently, tension between the US and Iran has risen again. Immediately following remarks by U.S. President Donald Trump suggesting the possibility of ending the unstable ceasefire agreement between the two nations after Iran’s attack on ships in the Strait of Hormuz, the U.S. military announced that it had conducted airstrikes on approximately 90 targets across Iran on Wednesday, July 8, 2026. In retaliation, Iran attacked U.S. allies throughout the Middle East. A series of attack alerts were issued for Qatar, Bahrain, Kuwait, and, a few hours later, Jordan, with both sides accusing each other of violating the terms of the ceasefire agreement. Moreover, Iran declared the Strait of Hormuz closed on Sunday, July 12, 2026, citing “hostile actions” and fresh strikes by the United States. [1]

President Donald Trump officially notified the U.S. Congress that U.S. “military action” against Iran had resumed on July 7, 2026,

Subsequently, the U.S. military officially announced on Tuesday, July 14, 2026, that it had resumed a blockade of Iranian ports in response to Iran’s attack on merchant ships in the Strait of Hormuz. This is a measure taken by the United States amid growing concerns over the resumption of all-out war following the near collapse of the ceasefire agreement.

The U.S. began a blockade of Iranian ports for the first time in mid-April 2026, but lifted it in mid-June, the day after the signing of an interim ceasefire agreement aimed at ending the war. This ceasefire agreement stipulated that negotiations on Iran’s nuclear program be completed within 60 days, but negotiations stalled as fighting between the two nations intensified over the Strait of Hormuz. On Monday, July 13, President Donald Trump announced the resumption of the blockade on Iranian ports and stated that he would impose a 20% toll on ships passing through the Strait of Hormuz. However, just hours before announcing the resumption of the blockade, President Trump withdrew the toll collection plan, citing requests from Gulf allies. [2]

These recent clashes between the two nations in early to mid-July have cast uncertainty over the fate of the peace agreement aimed at ending the war. Nearly half of the 60-day ceasefire period, during which the negotiating teams of both countries set a final agreement, has passed.

Under the ceasefire agreement, Iran agreed to waive transit fees for the Strait of Hormuz for 60 days, but it did not specify the situation thereafter. Iran claims the authority to manage transit and impose tolls, but the United States strongly opposes this.

Under this situation where war between the U.S. and Iran has resumed, the Houthis in Yemen, which had been quiet for some time, launched a missile attack on Abha Airport in southwestern Saudi Arabia on July 13, 2026. This was a retaliatory measure against Saudi Arabia’s airstrike on Sana’a Airport in Yemen. [3]

As Figure 1 shows, the Iran-backed Houthis, which control northwestern Yemen, condemned Saudi Arabia’s attack on the Sana’a Airport runway as a “blatant act of aggression.”

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Figure 1: Map of Yemen (source: CFR)

These exchange of attacks can be seen as the most significant escalation in the conflict between the Houthis and Saudi Arabia, which had been largely dormant since an unofficial ceasefire took effect four years ago.

Yemen has been devastated by a civil war that began in 2014 when the Houthis ousted the ruling government from the capital, Sanaa. The conflict intensified further in 2015 when a Saudi-led Arab coalition intervened in the Yemeni civil war to restore and reinstate the ousted government.

The Houthis rapidly transformed from a local insurgent militant group within Yemen into a state-level armed force possessing a powerful and continuously growing military power. [4] Supported by training, intelligence, and weapons from the Iranian Revolutionary Guard Corps (IRGC) and Hezbollah, the Houthis seized control of key Yemeni infrastructure, such as the port of Hodeidah in Sanaa on the Red Sea coast. Leveraging this influence, the Houthis launched attacks on the Red Sea region, including assaults on merchant ships passing through the waters between 2023 and 2025, and have endured retaliatory attacks from the United States and the United Kingdom in response.

The Houthis threatened to participate in the US/Israel-Iran War that broke out on February 28, 2026, implying that they had the capability to deploy the necessary resources for the conflict. In fact, the Houthi rebels officially intervened in the war on March 28 by launching ballistic missiles toward Israel. However, since then, they have remained quiet, refraining from attacks against Israel.

With the blockade of the Strait of Hormuz back in place by the resumption of fighting between the US and Iran, the exchange of fighting between Saudi Arabia and the Houthis raised concerns that the Houthi rebels could open another front in the US/Israel-Iran War by attempting to blockade the Bab el-Mandeb Strait (32 km wide), which they once targeted during the 2023 Israel-Hamas War. The Bab el-Mandeb Strait, one of the world’s busiest maritime routes along with the Strait of Malacca and the Strait of Hormuz, is the only gateway from the Indian Ocean into the Red Sea.

Indeed, the British Telegraph reported on July 15, 2026, that Yemen’s Iran-backed Houthis are coordinating with the Somali militant group al-Shabaab to lay the groundwork for a blockade of the Bab el-Mandeb Strait. [5] And finally, on Monday, July 20, 2026, the Houthi leadership declared that they would immediately implement a naval blockade against Saudi Arabia.

Based on this background, this paper aims to analyze, first, how the Iranian-backed Houthis were formed; second, what influences the Houthis have exercised both within and outside Yemen; and third, whether the Houthis will carry out a complete blockade the Bab el-Mandeb Strait this time in alignment with Iran.

 

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