The killing of Iran’s General Qassem Soleimani in a United States airstrike marks a major increase in tension between the two countries. Many fear the incident could lead to war and instability in the Middle East. Soleimani was head of Iran’s Quds Force, which has military operations in several countries in the region. The Quds Force is recognized by the U.S. as an organization that provides support to terrorism. Some considered Soleimani the second most powerful person in Iran behind Supreme Leader Ayatollah Ali Khamenei. Soleimani was killed along with several others Thursday near the Baghdad airport in Iraq. U.S. military officials said President Donald Trump ordered the strike to protect Americans. In a statement, officials noted, “General Soleimani was actively developing plans to attack American diplomats and service members in Iraq and throughout the region.” In Iran, thousands of people marched in Tehran and other cities to protest the killings.