English: For military purposes, cold regions are defined as any region where cold temperatures, unique terrain, and snowfall have a significant effect on military operations for one month or more each year. About one quarter of the earth’s land mass may be termed as severely cold. In Figure 1-2, this area is indicated by the area above line A in the Northern Hemisphere and below line A in the Southern Hemisphere. In these areas, mean annual air temperatures stay below freezing, maximum snow depths exceed 60 centimeters, and ice covers lakes and rivers for more than 180 days each year. Another quarter of the earth is termed moderately cold. In Figure 1-3, this area fits between lines A and B (including most of the United States and Eurasia). Its mean temperatures during the coldest month are below freezing.