Yemen's most recent bout of warfare erupted five years ago when the Houthis took over most of the nation. After the Houthis seized power, Saudi Arabia and the United Arab Emirates attacked them.
The foreign coalition had two objectives. First, it wanted to restore the toppled leader, Abdrabbuh Mansour Hadi. Second, it sought to prevent Iran from expanding its influence in Yemen. As of early 2020, the foreign coalition has utterly failed, and the Houthis remain in control of most of the devastated country. The UAE withdrew its troops from the costly and inconclusive war last year, but the Saudis continue to wage a fruitless war.
The warfare, instability, and misery that have afflicted Yemen over the past five years are not an aberration. Yemen has a troubled history. Its problems are caused by many factors. First, it is an extremely poor nation, and its poverty has bred political instability. Second, foreign nations have repeatedly intervened in Yemen's affairs. Saudi Arabia and the UAE were hardly the first foreign nations to interfere in Yemen. Britain and Egypt were active in Yemen as recently as the 1960s. Egypt's long and disastrous war in Yemen proved to be its "Vietnam." Third, Yemen has had a history of political disunity. Two separate Yemeni states formed a single nation in 1990, and it has been a turbulent nation torn apart by factions. Finally, terrorists have been active in Yemen in recent decades. For example, the USS Cole was attacked there in 2000 by al-Qaeda. For these reasons, the situation in Yemen is not likely to improve anytime soon.