Four in five vessels talk their way past Bab el-Mandeb

Since the July 20 blockade announcement, 141 out of 175 tanker transits through the Bab el-Mandeb strait have included free text in the destination field, with an overwhelming majority (81%) carrying messages about armed guards, flag or crew nationality, and cargo information. The messages are addressed to whoever is monitoring the Automatic Identification System (AIS) from the Yemeni coast, signaling their intentions to avoid a target set by the Houthis.

Three main intents emerge from the signaling messages: deterrence, affiliation, and cargo disclaimers. Deterrence is the loudest and least specific, with 29 transits announcing armed or private security teams aboard. Affiliation is more telling, with 21 transits volunteering a nationality, mostly Chinese. Cargo disclaimers are the rarest and sharpest, eight transits stating what the cargo is not, such as "NO SAUDI CARGO" or "NO LINK ISR/US/UK."

These disclaimers reveal the exact thing the sender is trying not to be caught carrying. The destination field is self-reported and unverifiable, so cross-referencing it with tracked cargo origin provides a readable signal. Ships carrying genuine Saudi crude either don't attempt the strait or cross without broadcasting any cargo-related messages, while those with Chinese or Russian ties openly state their affiliation.

This signaling behavior provides valuable intelligence on the intentions of vessels passing through the Bab el-Mandeb strait.