Weaponry or war?
Weaponry effects how people are killed in war, not how many. It also applies to the ability to hunt.
War has led to a great many advances in transportation and medicine.
" there would never have been nowhere near the number of casualties as what happened in reality"
That isn't necessarily true.
It is estimated that over 7 million Germans were killed in WWII. They had 24000 troops
In Desert Storm, Iraq had 1,000,000 troops, yet only lost around 100,000, and far fewer civilian casualties.