Why were snipers so effective in the Battle of Stalingrad?

Snipers of the Soviet Union played a useful role mainly on the Eastern Front of World War II, apart from other preceding and following conflicts. In World War II, Soviet snipers used the 7.62×54mmR rifle cartridge with light, heavy, armor-piercing, armor-piercing-incendiary, zeroing-and-incendiary, and tracer bullets. Most Soviet World War II snipers carried a combat load of 120 rifle cartridges in the field.

for this case we have the following equation:

we apply distributive property to the terms within parentheses.

subtracting 2 on both sides of the equation: