Bill mentions his time in the military in at least two episodes that I am aware of, RB-020 "If the Lord Is For Us Who Can Be Against Us" and also RB-009 "Bim, The Dog."
In "If The Lord Is For Us..." Bill encourages discouraged, young Army serviceman Ted Sloan. Bill tells of his persecution as a Christian by his sergeant during his training to fight overseas and how he was able to endure and benefit from that trouble. Bill was a Navy medic attached to a Marine unit training at New River, North Carolina.
Bill's sarge was Buck Donovan. Buck was tough and thought Bill was a "religious Lilly." Buck made life tough constantly for Bill in Big and little ways. Buck made Bill train harder than the rest of the men. He shorted Bill's supply requests or forgot them all together. Buck hid Bill's time-off passes for rest and recreation. And we need to remember that Bill's forest ranger dad had also passed away just weeks before Bill entered the service.
Bill finally won Buck over when he saved Buck's life when Buck was bitten by a rattler while the unit was out on maneuvers in a swamp. Buck's rough treatment of Bill probably saved his life because Bill was physically strong enough to carry Buck to an ambulance.
"Bim, The Dog" is actually a collection of real-life dog stories combined into this one Ranger Bill adventure. Part of that story is how Bim served with Bill in the fierce fighting in Bougainvillea Island in the Solomon Islands during WWII. In this story Bill and his unit are under attack by machine guns in a bunker. Bim was able to save the unit by jumping into the bunker and attacking the gunners allowing Bill's unit to overtake the Japanese. Bim is wounded and sent home.