International relations is not, as former president Donald Trump would like us to believe, purely transactional. States, particularly great powers, often do things that follow a political rather than an economic logic. Great powers provide public goods for their allies, even if those allies sometimes free ride. They maintain a network of bases and military forces stationed in foreign countries, and offer allies and friendly states various trade deals. President Trump’s business approach to international relations often overlooked or ignored many of the nuanced norms of international politics. This was particularly visible when it came to the arms trade, where Trump’s focus on the bottom line ignored the political consequences of arms sales, which are one of the many tools in the foreign policy repertoires of states, and are often used to express political alignments. For example, in 2019 the U.S. sent Javelin missiles to Ukraine to express support for Ukraine and against Russian aggression, a message which was sent and received even though the missiles were never intended to make it to the front lines. Trump’s transactional approach ignored the political-signaling function of arms sales, which will have lasting effects on U.S. political relationships. The Biden administration will need to quickly consider how best to adjust U.S. arms sales policies to align with its foreign policy goals and reassure allies of continued U.S. commitment.