It is impossible to create a one-stop comprehensive source regarding all World War II uniforms and equipment, even for one nation, let alone only the major nations (Great Britain, Germany, Canada, the United States, the Soviet Union, and Japan). Because the war was fought around the world, many variations in uniforms and equipment existed.

Shirt ButtonAs a result of financial cutbacks to the United States Army during the inter-war period, the standard uniform combined elements of both the basic dress uniform and the basic field uniform. By combining the uniforms, it was thought that time and money could be saved. The "Class A" or dress uniform consisted of an olive-drab (OD) wool garrison cap, olive-drab wool trousers, an olive-drab wool shirt with a khaki cotton tie, a wool olive-drab four button tunic, and russet brown Type I service shoes. The "Class B" or garrison uniform consisted of the above, minus the tunic.

The basic field uniform consisted of the basic wool uniform, without a tie, and with a field jacket. Footwear consisted of a basic low quarter tanned leather shoe used with heavy canvas leggings. Soon after the start of the war these shoes, which were also used as part of the Class A dress uniform, were replaced with a similar "roughout" version made from leather with a suede finish. Later in the war these shoes were in turn replaced by a higher boot with a buckled ankle flap that replaced the unpopular canvas leggings. Although other uniform parts were in use, the basic wool uniform saw the most use and had the greatest functionality, being able to keep the soldier warm in the winter with its insulation and cool in the summer with its breathability.

A second and less common uniform, the Herringbone Twill (HBT) uniform was made up of heavy cotton weave. Initially it was meant to be worn over the basic wool uniform to provide greater warmth, but it proved to be better suited for hot weather climates than the wools and was more often than not used by itself under these conditions. It was also issued in training as "work fatigues".

Because combat was unpredictable, supply and circulation in all theaters of the war gave some soldiers (usually in the rear) more than enough amenities while giving men near the front barely any. As a result of this, it is impossible to declare a basic combat uniform for World War II. Variations of all types exist, and can be seen in the European Theater of Operations. By D-Day, the M-1941 Field Jacket was predominantly seen, along with the full wool uniform (see above) and/or a mix match (depending on the unit and how it was supplied) with HBT parts of clothing. The M-1943 uniform was also issued to paratroopers, just in time for Operation Market Garden in Holland, September 1944.
As the Allies pushed eastward, photographs show evidence of more M-1943 jackets being worn, due to the high rate of replacements cycling in to replace dead and wounded soldiers. For example, browsing through photographs of the Battle of the Bulge, one finds photographs of soldiers wearing only the M-1941 Field Jacket, the M-1941 Field Jacket with the heavy wool overcoat, and the M-1943 Field Jacket. Officers can be seen wearing the M-1941 or M-1943 with the officer's overcoat, a khaki and lighter version of the enlisted heavy wool OD overcoat.

The dress uniform varied at different periods and places during the war, as well as varying by a soldier's rank and status in the military. Earlier in the war, virtually all soldiers (officers and enlisted men) wore a four pocket tunic modeled after the Royal Air Force tunic worn by the British RAF. While officers had a darker, finer made tunic with cut pocket flaps, the enlisted men wore general issue tunics with square pocket flaps; partially due to the fact that enlisted men generally did not have access to custom made uniforms. The "earlier" uniform also included a Sam Browne belt. The shirt and trousers of the "earlier" uniform consisted of the basic mustard wool uniform (as mentioned earlier). The uniform also included polished russet brown shoes (Type I), and an overseas cap.
The "later" uniform (focusing on the European Theater of Operations) consisted of the famous Ike jacket with the above mentioned uniform parts. In some cases (generally in the case of an officer), trousers were substituted with a chocolate brown colored trouser. Also, as GI's were issued "combat" boots later in the war, it became the fashion to wear the boots polished with the trousers bloused, or tucked, into the boots.