Most likely, the first war in human history was one group of guys rushing at another group of guys, swinging fists and anything they could use as a club. It did not take long before a man decided that it was a good idea to use his hunting weapons to ward off these attacks or compliment these attacks. After all, if a gang of men with spears could take down a large animal, the same tactics would work on humans. From there the arms race was on among the human species.
The club was probably the first weapon of war. The spear would be the first tool converted for use in war. The shield was the first tool of war created specifically for use in combat against other men. Unlike the club, the shield was not just lying around waiting for a man to use it in a fight. Unlike the spear, the shield was not something used for hunting. The shield was a practical response to men using their spears to poke at you in a fight. It was the dawn of the arms industry.
We have no way of knowing if any of that is true. The first men were not big on writing stuff down so we are left to speculate. Maybe the crazies are right and people are naturally peaceful until a weapon is introduced. Some guy brought his spear to the clan meeting and this caused the clans to break out into warfare. Perhaps humans were vegetarians, eating what they could find until one guy picked up a stick and then immediately decided to start beating people with it.
Putting that aside, the history of war has been one side finding new ways to get around opposing defenses, while the other side finds new ways to block or reduce the weapons the other side is using. We are seeing this in Ukraine as the Russians work through the puzzle that is the Ukrainian defense network. For close to a decade the United States worked with Ukraine on their tactics, defenses and training. The Ukrainians were as ready as they could be for this war.
One of the first problems the Russians faced was the well designed Ukrainian air defense system. This was a carry over from the Soviet days. During the Cold War, the Russians planned to defend themselves against superior American airplanes, so they designed advanced air defense systems. These things are always hotly debated, but the consensus is that the Russians are the best in the world at building surface-to-air missile systems for defending against planes and missiles.
Of course, this was the same problem presented to NATO. The Russians have even better air defense systems than the Ukrainians. They can take out the best aircraft from great distances. This is why the Pentagon was adamantly against imposing a no fly zone over Ukraine. Losing billion dollar aircraft on a daily basis is a good way to lose popular support for a proxy war. It is also why there was never any thought about training Ukrainian pilots on the F-35.
That is the first lesson of this war. Outside of asymmetric wars, like America attacking a weak country, manned combat aircraft is becoming obsolete. Surface-to-air missile systems are reaching the stage where they can defeat the best manned aircraft at pennies on the dollar. If you can take out a billion dollar plane with a million dollar missile, it is not going to take long before the other side stops using their billion dollar planes to attack you.
That is another lesson of the war. Wars between peers are about economics, not flashy displays of technological prowess. Each side must try to reduce the per unit cost of destroying the opponents assets and defending its own assets. Assuming equal number of assets at the start, the game becomes a contest of efficiency. The side that can run the war most cost effectively wins. We are seeing that in Ukraine as the frugal Russians grind down the extravagantly financed Ukrainians.