A brigade is a major tactical military formation that is typically composed of three to six battalions plus supporting elements. It is roughly equivalent to an enlarged or reinforced regiment. Two or more brigades may constitute a division. Brigades formed into divisions are usually infantry or armored (sometimes referred to as combined arms brigades). In addition to combat units, they may include combat support units or sub-units, such as artillery and engineers, and logistic units or sub-units. Historically, such brigades have sometimes been called brigade-groups. On operations, a brigade may comprise both organic elements and attached elements, including some temporarily attached for a specific task. Brigades may also be specialized and comprise battalions of a single branch, for example cavalry, mechanized, armored, artillery, air defence, aviation, engineers, signals or logistic. Some brigades are classified as independent or separate and operate independently from the traditional division structure. The typical NATO standard brigade consists of approximately 3,200 to 5,500 troops. However, in Switzerland and Austria, the numbers could go as high as 11,000 troops. The Soviet Union, its forerunners and successors, mostly use "regiment" instead of brigade, and this was common in much of Europe until after World War II.