On September 5, 2021, an American-trained military officer in Guinea’s armed forces led a coup d’état to oust President Alpha Condé. Though far from the only coup initiated by forces with American training, this coup marks the first time that someone has led a coup while taking that training. American officials have tried to distance the United States from the coup by saying that it is “inconsistent with U.S. military training and education” and suspending military support to Guinea. Weak excuses like this, however, cannot obscure the truth: U.S. military assistance and weapons sales to fragile nations like Guinea routinely enable and amplify violent outcomes.

The United States provides countries like Guinea with security assistance and weapons in order to improve the competence and professionalism of their militaries. The hope is that this will help stabilize the government and, in many cases, help the government confront insurgencies or terrorist groups. Unfortunately, however, academic research finds that military coups are more common and more successful after the military receives external support. Military aid and training shifts the balance of human capital away from the country’s government and towards their military. As a result, the military becomes competent enough to overwhelm other, weaker institutions of the country.

In countries that are already unstable and dealing with significant political turmoil, even a relatively small amount of external support can tip the scales. Over the last decade, for example, the U.S. authorized $4.8 million in weapons sales, provided $9.06 million in security assistance, and trained 1,326 soldiers in Guinea. Most of the training was for peacekeeping operations and the rest focused on combatting terrorism and general military education and training.

Nor is Guinea the only West African country to suffer the unintended side effects of American assistance. Guinea’s coup makes the fourth military takeover in West Africa in just the last year, following two coups in Mali and a disputed succession in Chad. The United States has trained over 6,000 troops in these countries in recent years.

Given the risks associated with security assistance and arms sales, we created the Arms Sales Risk Index. The index, based on a series of metrics regarding state stability and behavior, provides every nation a score from 1 (lowest risk) to 100 (highest risk) assessing the likelihood of negative outcomes like coups, the misuse of weapons by the government, the theft or sale of weapons on the black market, etc. Guinea’s 2020 risk score of 55 signals moderately high levels of risk. Of particular note, Guinea ranks as one of the fifteen most fragile countries in the world. That alone should have given the United States pause when considering whether and how to provide military assistance and weapons to Guinea.

Moving forward, the Pentagon should rethink its strategy of providing military assistance to countries with weak institutions. What seems like a low cost way to combat terrorism and improve stability too often ends up amplifying violence and destabilizing already unstable situations. Avoiding these situations lets the United States adopt a more restrained foreign policy by reducing situations of potential entanglement and support for human rights abusing governments.