Saudi-led intervention in Yemen (2015)
A Saudi-led coalition began a military campaign in Yemen against the Houthi movement, which had seized the capital Sanaa. The war drew in regional powers and became a long attritional conflict.
The coalition failed to quickly dislodge the Houthis, and the conflict dragged on for years.
The Houthis built up missile and drone capabilities that they have used to strike Saudi airports and oil facilities, shaping Riyadh's search for regional security partners.
Saudi Arabia's renewed war against the Houthis is the immediate backdrop to its defence agreement with Syria and its requests for military support from partners.
