There had been a lot of technological advancements since 1914 (tanks, faster tanks, dedicated fighter, bomber and ground-attack aircraft, aircraft-guided artillery, better artillery, rolling barrages, easily portable machineguns), none of them were enough individually to break the deadlock of the Western Front. At Paschendale in 1917, for example, the Allies used combined arms well, but the attack still got bogged down in mud and fierce resistance.

What really swung the balance in 1918 was that the German army had utterly exhausted itself, especially during the Ludendorff Offensive, when they really flung everything they could at the Allies. Although this attack made significant advances, the Allies countered it well, deploying their reserves to hold the Channel ports and Amiens whilst essentially allowing the Germans to break through and capture swathes of strategically useless ground, thus overstretching their logistics and leaving them vulnerable to counterattack. This bought enough time for the recently arrived American forces to be properly deployed as massive fresh reserves for a counterattack, whilst the over-stretched German army simply didn't have the resources to dig in and consolidate the gains it had made.