It was September 1983, and a young senator named Joe Biden had a message for President Ronald Reagan. “I would not support any authorization for troops in Lebanon of any duration absent much more clearly defined goals and a reasonable prospect of attaining those goals,” Biden said, commenting on a proposed congressional war powers resolution. U.S. Marines had been deployed to Lebanon as part of peacekeeping mission in the wake of an Israeli invasion aimed at destroying Palestinian militias, and Congress was debating whether to continue the mission. A month after Biden’s warning, a truck bomb k…