He helped established the think tank in 1962, and interrupted his work there several times to work for various Republican administrations.
Here is more from The Washington Post:
After working at a predecessor to the American Enterprise Institute, he joined retired Navy Adm. Arleigh Burke in founding CSIS. Once associated with Georgetown University, it grew into a think tank whose members include Kissinger and former national security advisers Zbigniew Brzezinski and Brent Scowcroft.
Here is a statement from CSIS on Dr. Abshire's death. Here is a statement from Sen. Bob Corker (R-TN).
CSIS has the Abshire-Inamori Leadership Academy (AILA) to provide rising global leaders with training opportunities in leadership, ethics, and foreign policy. Dr. Kazuo Inamori was the founder of Kyocera Corporation.
CSIS's other co-founder, Arleigh Burke, died in 1996. The think tank still has the Burke Chair in Strategy that provides political and military analysis of challenges facing the US and the world. Anthony Cordesman is the current Arleigh A. Burke Chair in Strategy.
In related news, Bill Taylor, former head of CSIS's International Security Program, recently passed away.