The german high command in 1918, wary of the imminent entry of the US in the war, decided to
try and knock off the entente as quick as possible before the americans could enter instead of offering peace negotiations. The subsequent series of manoeuvers was known as the Spring Offensive.
However, the generals were unsure of where exactly to attack, and such undecisiveness cost the germans a huge price. Later that year, WWI was over.
But what if the germans had decided to focus on the rail hub of Amiens?
The rail hub was a vital supply link between the french and the british, running towards Calais. Had the germans been successful in taking such a territory, the supply link could be broken, and Calais would be in big trouble. The french and british would have to instead rely on the west of the english channel, but even that would be difficult as winter was approaching and the ports in Normandy and southern England could end up freezing. This would give the germans an enormous advantage.
Would a successful capture of Amiens be enough for the germans to achieve their "quick victory" before the US comes in, or would it only delay the end of WWI into 1919/1920?