During World War II, each unit in the U.S. Army had an official table of organization and equipment (T/O&E). From *The Organization of Ground Combat Troops;

For each unit the T/O&E prescribed the number of its officers and men, the grade and job of each, the proportion of various occupational specialists, the arrangement of command and staff and administrative personnel, the means of transport and communications, the provisions for supply, maintenance, construction, and medical care, and the kind and quantity of individual and unit armament, together with the relationship between supporting weapons and consequently the tactics of the unit.

Here is the table of organization and equipment of a Ranger infantry company (7-87), dated 29 February 1944. It contains the unit's organizational charts, as well as numbers and types of equipment issued to the unit as a whole from the seven Technical Services or other parts of the Army.

Tables of organization and equipment could be revised periodically. If the change was small, a "change" could be issued to an existing T/O&E without changing its date. If the changes were large enough, a new T/O&E would be issued; with the same number, but a different date. There existed a difference between "organizational" equipment listed in a TO&E and other pieces of materiel that were "personal;" either issued to the soldier before ever being assigned to a unit because he is such, or able to be issued outside of an organizational format, in lots to divisions, for example. Boots and helmet nets were some of the latter.

Each soldier in the United States Army was supposed to maintain two pairs of boots, one for garrison use and one for field use. From the mid-1930s until early 1941, soldiers were issued either "garrison" or "service" shoes, a grain side out leather ankle-length boot. The garrison shoe had a rubber heel and leather sole, while the ground contact surface of the service shoe was entirely leather; otherwise, they were basically the same. After it was found that the leather heels of the service shoes wore through quickly, a shift was made to rubber, along with other improvements, resulting in the replacement of both shoes by the Composition Sole Service Shoe (externally extremely similar in appearance to the previous types), of which there were three types, the first being the "Type I" service shoe. The same wear problem was encountered with the Type I, except on the ball of the foot, so in September 1941, the Type II service shoe with an entirely rubber sole was introduced. Procurement of the Type I ceased in December 1941. In January 1943, the Type II shoe was redesigned with the flesh side of the leather facing out ("roughout") due to the ability of the flesh to accept waterproofing compounds, becoming the Type III. Deliveries of the Type III commenced in April 1943, and it was approved for overseas use. Simultaneously, the Type II was only to be issued within the continental United States. In January 1944, the Composition Sole Combat Service Boot was approved for production. It was essentially a Type III service shoe with a buckled leather cuff fastened above the ankle, intended to replace the awkward M1938 dismounted leggings. The Type III and Composition Sole Combat Service Boot were produced concurrently until the end of the war. Dates of approval and first production never match combat introduction; the Type III service shoes first appeared just before D-Day, and the Composition Sole Combat Service Boot appeared in the fall of 1944.

I talk about helmet nets here.

More of courdse can be said, but do check out this old thread.