In the wake of previous attacks, both Russia and NATO would launch warheads toward each other's 30 most populous cities in the final stage of of the scenario, using five to 10 warheads for each city depending on its size.
This phase would cause 85.3 million casualties — both deaths and injuries. But the total casualty count from the entire battle (of less than 5 hours) would be 34.1 million deaths and 57.4 million injuries, or a combined 91.3 million casualties overall.
But that's just the immediate conflict: The entire world would be affected by nuclear disaster in the months, years, and decades to come.
The radioactive fallout from the nuclear disaster would cause additional deaths and injuries. Studies also suggest that, even with a limited nuclear engagement, Earth's atmosphere would cool dramatically, driving famine, refugee crises, additional conflicts, and more deaths.