Conflict Arms Research has produced this report saying that, between February 2019 and July 2021, CAR investigators worked in Afghanistan to document illicit weapons in the country. It says that very little attention has been paid to the group’s long-standing ability to exploit weaknesses in US and Afghan government controls over weapon supplies. Taliban access to weapons and ammunition intended for Afghan security forces is not new, but it has expanded significantly over time and was less reliant on external sources than might have been supposed. It warns that recent events in Afghanistan highlight the need to address persistent challenges and weaknesses in the US supply of weapons, ammunition, and military equipment to other government-backed forces in other countries affected by armed conflict and terrorism. This report is the first in a series that will draw out key findings from CAR’s Afghanistan data set. It explores the long-standing capacity of the Taliban and other armed actors in Afghanistan to access weapons that had been supplied by the US and NATO to Afghan forces, and considers the systemic challenges that have enabled weapon diversion from national custody in the past. It focuses on small arms and light weapons and does not delve into issues around the seizure of aircraft or other equipment.