The weapons shown are accurate for the Red Army at the time and include PPSh-41 submachine guns, DP-27 light machine guns, SVT-40 semi-automatic rifles, and M91/30 sniper-variant Mosin-Nagant rifles.
The name of the half-submerged boat in the first scene appears to translate as "Indestructible". (The last characters are unreadable.)
In this Secret War, it is a battle that happens entirely within Russia. In real life, "The Secret War" quoted by the CIA refers to the covert operations the U.S. conducted in Laos to fight against communist regimes, including Soviet Union Russia.