Returning Soldier Effect

The paragraph under subheading “Sex ratio without war” doesn’t sound right, it seems to imply more men are born as a result of higher mortality rate but doesn’t really make sense, how can mortality rate influence sex ratio at birth? In the general population sure. Or it’s just poorly written and is referring to sex ratio in the population in an article about birth rates.

"The returning soldier effect is an observed phenomenon where more boys are born relative to the number of girls after periods of war."