L-trains existed already in the era of the former state railways. These L-trains were exploited by the CIWL (Compagnie Internationale des Wagon Lits). This company, founded in 1876 and settled in Paris exploited many international trains. These trains were always very luxurious. That's why the name of these trains was L-trains, with the L of Luxus. The trains were also called Pullman trains. Trains like the Orient Expres and the Flèche d'Or were exploited by the CIWL.
The DRG had to gave passage to CIWL trains after the first world war. And these trains must achieved the same speed as domestic trains of the DRG. As a result of these regulations the Germans founded their own company for luxurious trains on 24 November 1916, the company was named Mitropa.
During epoch II most L-trains were exploited by the CIWL. However three trains were exploited by Mitropa, but this was for short. L-trains consisted mainly of sleeping cars, dining cars and salon cars. Most of the coaches were of the Pullman type of the CIWL.
The locomotives which had pulled the L-trains were mostly the better former state railway locomotives of the group 11 upto 19 and later on standard design locomotives, see also locomotives epoch II.