A group of rebels once known as Iran's "merchants of chaos" have moved on strategic islands in the Red Sea and are now putting one of the richest and most powerful nations in the Middle East in a tricky spot.
After a years-long stalemate, the Houthis reignited their war with Saudi Arabia and the internationally recognised government this year, launching a lightning assault in mid-September that ended in the capture of Mokha, a port city, and the small island of Perim.
The seizure of the two areas gave the Houthis almost complete control of Yemen's Red Sea coastline, and put them within firing distance of any ships that tried to navigate the Bab el-Mandeb Strait.
The Iran-aligned group were quick to act on their strategic advantage, firing at Saudi oil facilities on September 8 and tankers that tried to navigate the narrow strait.
Days later an attack on Saudi Arabia's east-west pipeline, blamed on Iran-backed militias in Iraq, sent shockwaves through the Middle East and rattled world markets.
As economists and traders began unpicking the implications of the group's actions on the global economy, the Houthis took another step on their escalation ladder, launching strikes on critical infrastructure in Saudi Arabia.
Unlike many other nations, Saudi Arabia escaped the initial months of the war between Iran and the United States relatively unscathed.
As fighting has escalated in recent weeks, the Saudis looked to their allies, the United States, to intervene, as it did before under the Biden administration and last year under Trump.