First there is the fact that, at the time of the Soviet empire, Russia built up a nuclear arsenal that, together with the USA, gives this country a unique position in the world. This is the position of 'mutually assured destruction' (MAD). This means that the country has the capacity to completely destroy the opponent in the event of a nuclear attack on its own territory. No other nuclear power outside the US has that capacity today.
Why Russia is militarily strong. First there is the fact that, at the time of the Soviet empire, Russia built up a nuclear arsenal that, together with the USA, gives this country a unique position in the world. This is the position of 'mutually assured destruction' (MAD). This means that the country has the capacity to completely destroy the opponent in the event of a nuclear attack on its own territory. No other nuclear power outside the US has that capacity today.