Yemen civil war 2015 to present.
Presidency Trump January 20, 2017

I think the sorry saga started on the democrat watch under Obama.
Just one more inherited situation for Trump to contend with.

Saudi Arabia and the United States have a relationship that stretches back almost a century, since the 1933 kickoff of oil exploration in the kingdom.

Since then, the two countries have maintained a baseline of economic and security cooperation that has kept ties between them strong. Saudi Arabia is the US' largest foreign military sales customer, and the US has long had a physical and advisory military role in the kingdom.

Perhaps a partial antidote to the starvation in the Yemen would be for the US to cease aiding the Saudis.

I cannot say I am totally clued up on the politics but I believe the Houthis booted out the previous corrupt regime based in Saana and ever since the Saudis and their allies have done their best to destroy the country.
" The military coalition led by Saudi Arabia and the United Arab Emirates in Yemen has killed thousands of civilians in airstrikes, tortured detainees, raped civilians and used child soldiers as young as 8 — actions that may amount to war crimes, United Nations investigators said in a report issued Tuesday."(aug28 2018 NYT)

The country was poverty stricken when I was there around 2000 and since then the situation has deteriorated dramatically.
I cannot say that I have seen a cogent reason as to why the Saudis are there. The Houthi receive help from Iran and are Shiite whereas the Saudis are Wahhabi Sunnis. The major powers are also fighting a proxy war there.
Meanwhile the war crimes continue, the people continue to die, starvation is imminent and nobody appears to give a shit.