The United States has a long tradition of arming its allies to advance Washington's foreign policy. In 1940, President Franklin D. Roosevelt called the U.S. the "arsenal of democracy" as he pledged thousands of ships, tanks and warplanes to countries battling Nazi Germany.
Roosevelt's characterization is no less true today. The U.S. government is sending large amounts of weapons to allies desperately battling Islamic State extremists in Iraq and Syria. Washington is also considering equipping the battered Ukrainian military, which has been fighting Russian-sponsored rebels in the country's east.
Broadly speaking, there are two ways the U.S. can arm an ally. America can donate, or sell cheap, the latest U.S.-made weaponry. Or it can send foreign-made weaponry — Russian usually — through a middleman.