How did the Houthis become so powerful?

On Sunday it looked like the United States was about to wade back into its fight with Ansar Allah, or the Houthis, the Iran-backed group in Yemen that has grown into a surprisingly powerful military presence in the region. Saudi Arabia had been asking for support after a series of Houthi attacks and advancements,  which brought a major global shipping and oil chokepoint - the Bab el-Mandeb strait - under Houthi control. Iona Craig has been reporting on Yemen and the Arabian Peninsula for over a decade and she joins us to track the group's rise from a group of rebels from the mountains of northwestern Yemen to a geopolitical force. For transcripts of Front Burner, please visit:  https://www.cbc.ca/radio/frontburner/transcripts