Historically war has consisted of three components: strategy, number of soldiers, and technology. Any war can be broken up into these three parts, but as you look farther and farther back in history, the component parts have different dominance. Technology can be as simple as a rock tied to a stick or as complicated as a super computer. With the evolution of technology there came the evolution of war and with that technology grew to have a bigger role in war.
Some examples of wars such as Alexander the Great and his conquests, the American Revolutionary war, or even tribal Warfare in un-colonized Americas were heavily dependent on the number of people fighting. Outnumbering your opponent or vice versa had a huge impact on the outcome. And then better strategies and technology plays in to compensate. In tribal warfare, the tribes would usually have similar strategies, using the terrain and their equipment efficiently, so the bigger component would be the manpower and numbers in the tribes. During the american revolutionary war, the Continental army was outnumbered and less armed. In a sense they had a disadvantage in numbers and technology. So during the battle of Seratoga, using the terrain and small trenches to their advantage they suffered half the casualties as the British even though they were outnumbered.
As time moved on technology and weaponry evolved. The first World War implemented the use of planes, warships, and machine guns. Even though the number of soldiers an army had was very important, the war could be dominated by a side that had more planes for example. They would bomb cities and require a small relative number of pilots. During the trench Warfare, the equipment, number of soldiers, and strategies of any side offered no specific advantage, hence much of the trench warfare was a stalemate. The German scientists then created gas weapons such as mustard gas, which gave them a huge advantage as they could simply launch canisters into enemy trenches and wreak havoc.
The second World War followed an even bigger dominance of technology. Hitler prepared for the War by amassing planes, warships, submarines, and tanks. His famous war tactic was Blitzkrieg, which consisted of planes bombing from the skies, and tanks plowing the streets followed by soldiers. With his superior technology and strategies he could theoretically win outnumbered 100-1 if the enemy side didn’t have the same weapons. In addition to this, the war being fought between Japan and the US consisted of naval and air forces. The island hopping warfare in the Pacific did little in the large scheme of things because both countries were evenly matched with their technology and tactics. However, when arguably the biggest advance in warfare technology, the Atom Bomb was used, it showed the world how a weapon could do so much damage with so little manpower. And not long after the second World War finally ended.
The Cold War was fought with few relative casualties aside from proxy wars. The grand scheme of the war was to amass the most technological weaponry. To have the biggest potential of destruction so that a side could win only by their power. The collection of nuclear missiles and weapons would do so much damage that both WARSAW and NATO avoided actually engaging. Hence the war was won almost entirely by technology. As humanity and its technology evolved, warfare became more dependent on technology.