Any student reading "Julius Caesar" in 2011 might have chuckled at the irony that Syrian forces had taken up arms and tried to kill President Bashar al-Assad on the ides of March. But the resulting unrest soon became no laughing matter. By 2015, the Syrian population was decreasing 2.3 percent, according to the World Bank. The European Union estimates that 11 million Syrians are displaced and 13 million are in need of humanitarian aid. The refugee crisis created by the civil war has sparked debates in Western countries about their roles in helping those in need. For many, Syria is the worst humanitarian crisis of the 21st century.

They may be wrong about that. The United Nations High Commission on Refugees estimates that 21 million Yemenis needed humanitarian aid and 2.5 million were displaced in October 2015, just a year after fighting in the country started.

The conflict is between the former government and the Houthis, a family that can trace its lineage back to the prophet Mohammed. Such families had made up an aristocracy in the country before Western-educated elites brought liberal democracy. In September 2014, the Houthis and their allies rose up against the government and took the capital, Sana’a. Saudi Arabia, Yemen’s powerful northern neighbor, became uncomfortable with the unrest along its border and stepped in at the request of ousted president Abd-Rabbu Mansour al-Hadi. In March 2015, the Saudis began conducting airstrikes against Houthi military outposts, but have since begun cluster-bombing whole Yemeni cities, resulting in thousands of deaths at a time. Diseases have run rampant, with cholera infecting 600,000.

Why is Saudi Arabia acting so carelessly? Many assume that Yemen is a proxy for the Sunni Muslim Saudis’ beef with Iran, whose leadership practices Shi’ite Islam. Iran has been selling arms to Houthi rebels, supposedly in an effort to prop them up in Sana’a. By invoking Iran, Saudi Arabia has convinced Israel and the United States that they do not need to worry about the crisis in Yemen because it is for a good cause: wrangling in part of the axis of evil, in George W. Bush’s words.

But that is not the real reason. Iran is not funding the Houthi war effort as many seem to think. Rather, Saudi Arabia has always been uneasy about Yemen. It is the poorest nation in the Arab world and has been in conflict almost since its founding. But perhaps most importantly, it is a democracy. The Saudi monarchy does not want its country to be infiltrated by liberal ideas, so the Saudis are making a deliberate attempt to cripple the country and undermine its influence.

As with everything else, U.S. President Donald Trump has only made things worse. On his last visit to Saudi Arabia (the one where he famously touched the orb), Trump negotiated a $110 billion arms deal with the Saudi government. The deal had technically already been negotiated by the Obama administration, and the Saudis are likely unable to afford the deal until oil prices rise, according to the Brookings Institution. But Trump seemed to want the arms to be sold in spite of Saudi Arabia’s demolition of Yemen.

The civil war in Yemen has started a humanitarian crisis that is destined to spill over into Europe and America the way the one in Syria has. U.S. citizens must educate themselves about the crisis, and U.S. policy toward Saudi Arabia must account for the realities of its intervention in Yemen.