John M. Collins began to amass military experience when he enlisted in the Army as a private in 1942. Thirty years and three wars later, in 1972, he retired as a colonel. He spent the next quarter century as the leading analyst on military and defense issues at the Congressional Research Service. Twelve years ago, he established the Warlord Loop, a by-invitation-only e-mail forum that fosters voluminous, freewheeling exchanges seven days a week. Resultant brainstorming is roughly equivalent to a graduate education in national security at no cost save time expended.