In 1923 the Marine Corps aligned its rank structure with the system used in the Army. This added a pay grade, which the Corps used to create the new rank of staff sergeant. The system of seven enlisted pay grades would remain in use for over thirty years. In 1925, the technical ranks were established for the first time. In 1935, cooks and bakers were aligned into the technical ranks, giving them a logical career progression.
World War II brought an explosion of ranks and titles. It was fairly straightforward for Marines serving in line billets. For those in technical or clerical duties however, the system mushroomed into a bewildering array of rank designations. The system was streamlined somewhat by 1944. The rank system below is that used in the latter part of the war.