“they say that when Ukrainians are sent to the front line,
their life expectancy is about 4 hours”
Or it may be an accurate assessment of the risks involved in very high intensity combat. That life expectancy has occurred in many other wars involving high intensity battles for the soldiers that are actually at the front of the fighting force.
Regardless of what army you are serving in, or what war, if you are storming a trench or a building with equally trained and equipped soldiers on the other side where both sides have mortars, IFVs, tanks, and other assets your life expectancy is very short.