Major assigned to Stargate Command in its early years of operation. Warren traveled to the planet Chulak as a member of SG-2 under the command of Charles Kawalsky. He later commanded SG-3, and was subject to alien duplication by creatures that nearly took over Earth when Cheyenne Mountain was under a foothold lockdown.
Note: Actor Colin Lawrence's character is credited as "Major Lawrence" in "The Sentinel." Because he is still commanding SG-3 after nearly four years, we're presuming this is the same character as "Major Warren." For the purposes of canon, it's presumed that he may have changed his surname.
Children of the Gods - Warren serves on SG-2 under Major Charles Kawalsky, backing up SG-1 on the first mission to Chulak.
Prisoners - Warren commands SG-3 in an attempt to find SG-1, but learn that they have been imprisoned by the Taldur.
Foothold - Warren is one of the officers duplicated at the S.G.C. during a foothold incident by alien invaders.
Menace - Warren returns to Reese's homeworld with O'Neill where he and his team find dormant Replicator blocks.
The Sentinel - Major Lawrence (Warren) and SG-3 back up SG-1 on a mission to Latona, which is attacked by the System Lord Svarog.