How did the poorest country in the Arab World become one of the most important?

With a Houthi rebel insurgency in the north and a secessionist movement in the south, Yemen has not seen true stability nor all-encompassing governance in decades. 40% of its water supply is used to cultivate qat, an amphetamine that more than 70% of households in Yemen say have at least one user. Couple the deep cultural, political and economic significance of the drug (from use once a week by the wealthy to widespread use following economic expansion in the 1970s) with the declining water supply and a recipe for crisis emerges.