The war in Yemen has entered a new phase as Houthi fighters seek to take control of Marib, the only city in the north still controlled by the Saudi-backed Yemeni government. Yemeni scholar Nadwa Al-Dawsari tells host Carol Hills about this full-on assault by the Houthis, which comes as both the UN and the US urge a mediated solution to the war, now in its sixth year.