 Complete the following phrase:  Bombing and artillery cover Moscow as Razov, Filipov and Lambert race back to the Kremlin. Fighting their way inside the bunker, Razov takes control of the nuclear communicators and inputs a code. Lambert calls President Constanzo to tell him that Razov has agreed to the ceasefire terms. Razov explains to Constanzo that the code he entered had disabled the detonators on the nuclear warheads on board the Bastions submarines: a fail-safe measure established by Gorbachev after the 