According to Brookings Institution, some of the biggest foreign policy and national security stories of 2020 were:
The assassination of Iranian commander Qassem Soleimani by the United States
The signing of a peace agreement between the United States and the Taliban
The COVID-19 pandemic and its impact on global health and economies
The Black Lives Matter protests and their impact on race relations in the United States
The U.S. presidential election and its implications for domestic and foreign policy
I hope that helps!