Saudi Arabia has announced the formal launch of a multinational maritime defense coalition aimed at safeguarding shipping in the Red Sea and Gulf of Aden, as escalating hostilities with Yemen’s Houthis threaten one of the world’s most important trade routes.

Thirteen countries have completed the procedures required to formally join the alliance, while 15 have signed its joint statement, the Saudi Defense Ministry said on Thursday.

Riyadh described the development as the “actual launch” of the coalition and the beginning of its institutional and operational activation. Saudi Arabia will provide its first commander, while Pakistan is expected to appoint the deputy commander. The alliance is expected to coordinate intelligence sharing, joint exercises and maritime operations aimed at protecting commercial navigation in the Red Sea and Gulf of Aden.

The announcement comes amid a sharp escalation between Saudi-backed forces in Yemen and the Iran-aligned Houthi movement following roughly four years of relative calm.

Earlier this month, the Houthis announced coordinated ballistic missile and drone strikes against military camps belonging to Yemen’s Saudi-backed, internationally recognized government. The group said it acted after detecting preparations for an offensive against Houthi-held territory.

Government forces acknowledged casualties, while Reuters cited government sources as saying at least 30 soldiers had been killed.

Tensions have been building since July, when a dispute over direct flights between Houthi-controlled Sanaa and Tehran helped unravel the longstanding truce. After Saudi-backed forces struck Sanaa airport on July 13 to prevent an Iranian aircraft from returning a Houthi delegation from Tehran, the group blamed Riyadh, declared the ceasefire over, and subsequently announced a naval blockade of Saudi Arabia.

The Houthis have since claimed attacks on Saudi-linked shipping and oil infrastructure, while the Saudi-led coalition has struck Houthi military sites in Yemen.

The confrontation poses a particular threat to Riyadh because the Red Sea has become an increasingly important outlet for Saudi oil amid the US-Iran conflict and severe disruption to shipping through the Strait of Hormuz.

Saudi Aramco has redirected crude away from Hormuz through its cross-country pipeline to the Red Sea port of Yanbu. Loadings there have averaged more than four million barrels per day since June, more than four times the level recorded during the same period last year, Reuters reported, citing tanker-tracking data.

With oil and petroleum products accounting for more than three-quarters of Saudi exports, a sustained disruption of Red Sea shipping could therefore threaten a crucial alternative export route.

The coalition’s activation also comes amid reports that Riyadh is preparing for a potentially broader confrontation with the Houthis. The Guardian reported earlier this month, citing Yemeni sources, that Saudi-backed forces were being re-positioned for a possible sea and ground offensive.