was the Oklahoma City Bomber part of a militia

Not really sure. If anyone was true believer enough to keep his mouth shut, it was McVeigh. I honestly believe he minimized the two or three others involvement with his testimony.

On the other hand, I do sense a loner in him. He'd be around groups, fit in very well peripherally, then? Move on. The trip to Waco, the NW for Nationalist groups, but never stayed very long.

If I was to HAVE TO form a conclusion? My best guess would be this: He undoubtedly DID swap ideas with other like minded people. Maybe they even helped him with details of planning, hypothetical targets, 'how to', etc. In fact, when he was caught, I'm sure a few dozen folks acquainted with him had a "Holy shit, THAT GUY REALLY PULLED IT OFF!" moment, among dozens of other 'potentials'. He seems capable of doing it alone, and keeping the loop as small as possible.

The most disturbing thing about McVeigh was "A", he was very intelligent, and "B", far more resourceful than the average Joe. Ironic that he used his own name in that hotel.

I do believe this about McVeigh: he'd have done one of two things if he gotten away with it. Told some people he 'met along the way' about what he'd done, because, as crazy as it sounds, this was a labor of love for him. He honestly felt he was a 'hero'.

Or? Done a "Unabomber", and start plotting his next 'event'.

I don't know if it'll ever be sussed out fully. The fact he put all the blame on himself, and gave "name, rank, and SSN" about everything else doesn't surprise me.