Integrated Logistics Systems** (ILS) is the military jargon for a combined procurement and spares management and maintenance planning which conveniently encompasses a number of busy topics which are common to almost any organization which owns hardware and software and has to keep it operational. This "department" tends to consumes the most effort and funds of any in a capital intensive industry - such as chemical process industries, power plants, marine, aerospace and the military - but perhaps not manufacturing where the cost of raw materials tends to predominate.
Rather than have a "Procurement" SIG and a "Maintainability" SIG and a "Training" SIG and maybe a couple of others - the easily recognized ILS term was felt to be a more useful choice.
** some dummy substituted "support" for "systems" in Wikipedia - don't believe it.