It is estimated that over 60 million people died in World War II, making it the deadliest conflict in human history. The vast majority of these deaths were soldiers, and the countries that lost the most soldiers were the ones that were most involved in the fighting.

The Soviet Unionhad the highest number of fatalities of any single nation, with estimates ranging from 22 to 27 million. China then suffered the second-highest number of casualties, estimated at around 20 million, though these figures are less certain and frequently overlap with the Chinese Civil War. Over 80 percent of all deaths were from Allied countries, with the vast majority being civilians. In contrast, 15 to 20% were among the Axis powers, with the majority of these being military deaths, as shown by Germany and Japan's death ratios.

China was the second deadliest country, with an estimated 20 million military deaths. This is due to the fact that China was invaded by Japan early in the war, and also because China had a large population.

Germany was the third deadliest country, with an estimated 5.3 million military deaths. This is also not surprising, given that Germany was one of the main aggressors in the war, and was involved in some of the most brutal fighting.

The United Stateswas the fourth deadliest country, with an estimated 407,000 military deaths. This is relatively low, considering the size of the United States and its involvement in the war.

TheUnited Kingdom was the fifth deadliest country, with an estimated 383,000 military deaths. This is due to the fact that the United Kingdom was involved in the war from the beginning, and also had a large population.

These are the five countries that lost the most soldiers in World War II. The vast majority of these deaths were soldiers, and the countries that lost the most soldiers were the ones that were most involved in the fighting.