Two years before Joe Biden won the presidency, 30 national security experts who worked with him under President Barack Obama published a high-profile mea culpa. They called their policy of supporting the Saudi Arabia-led military campaign in Yemen a “failure,” citing how it hurt civilians, and urged then-President Donald Trump to end it.

The move had big implications for U.S. foreign policy. Critically, it acknowledged that Washington’s pattern of arming and aiding other nations made Americans complicit in their actions ― a truth that the Obama administration spent years denying with regard to Yemen.