IMT #1 was a single-round Core War tournament held in May 1998. It was inspired by and loosely based on round 4 of the Redcode Maniacs Tournament, held earlier same year by Philip Kendall and Christian Schmidt. The idea of IMT #1 was to explore the feasibility of "co-operative" strategies by placing P-switcher warriors in a situation resembling an Iterated Prisoners' Dilemma. The results of the tournament, though in some ways unexpected, clearly fulfilled that goal.
Note: The rules are specified as a set of changes to the rules of RMT round 4. They may not make much sense without this context.
Philip Kendall (who, incidentally, won the tournament) wrote a very nice article about it in Core Warrior 68.