i was wondering about that, i mean technically it could be considered the last war because it was before the modern era (1900) and yes,i know about world war and etc but what i mean is that the mexican-american war was the last one that didn’t have a lot of planning into it, similar to wars in the older days,like there was no system control back then or like radio so technically, while not true, could it be considered “the last war of humanity”?
It might seem like there was an “old days” in war compared to modern times but technology in war has always been continuously improving and has often been the decisive factor.
In the America-Mexico war the Americans had a distinct technological advantage being able to use the newer and more accurate 1841 Springfield rifle. They also had superior artillery technology.
If you mean the “old days” as in mass troop movement on the field and hand to hand fighting and no computers then there was plenty of that all over Europe and elsewhere later in the 1800s all the way up to WWI.
See the Crimea War 1853-1856 and the Franco-Prussian war 1870-1871 for some notable examples. (Both with rifles, troops marching on the battle field, cannons, horses etc)