Nuclear warfare (sometimes atomic warfare or thermonuclear warfare), is a military conflict or political strategy in which nuclear weaponry is used to inflict damage on an opponent. Compared to conventional warfare, nuclear warfare can be vastly more destructive in range and extent of damage, and in a much shorter time frame. A major nuclear exchange could have severe long-term effects, primarily from radiation release, but also from the production of high levels of atmospheric pollution leading to a \"nuclear winter\" that could last for decades, centuries, or even millennia after the initial attack. A large nuclear war is considered to bear existential risk for civilization on Earth. Importantly however, despite modern civilization being at risk, assuming weapons stockpiles at the previous cold war heights, analysts and physicists have found that billions of humans would nevertheless survive a global thermonuclear war.