Why did the Central Powers lose?

How is it that the Central Powers managed to lose the war when they had so much momentum in the beginning? German armies were able to overrun all of Russian Poland and had developed clorine gas, Russia was in turmoil and being severly weakened, and the Central Powers were winning battles left and right, all while the Allies were being increasingly weakened and defeated. Germany was using unrestricted submarine warfare which was extremely effective in wiping out entire navies. How did the war turn around? There are a few reasons that I can think of, the British blockade of supplies going to Germany, which we talked about in the other book was for sure a huge factor, but what else? That can't be the only cause, for sure, the entrace of the US into the war was significant, but not as significant and I believe it's made out to be. At the beginning of the war the Central Powers had so much momentum it's hard to believe they lost.

Pgs 102-115

This whole chapter was about WWI and I found it very interesting to go back and look at how the war played out after we had fully understood the causes. How the alliances played out and all the new technology was very interesting. I thought it was odd how although the German's had their U-boats that were so successful and they gained a great advantage after Russia dropped out of the war they still lost. Why? the book states a few different causes, the British naval blockade as I understand was the biggest factor, this blockaded Germany and although they resumed unrestricted warfare this seems to be too little too late? Question number 9, "Was Germaun "unrestricted submarine warfare" an avoidable mistake?" was quite confusing. A mistake on which side? Was using the sumbarine warfare a mistake on Germany's side because it wound up drawing the United States into the war? Or was it a mistake on the Allies side of the war beacuse they were using their navies so effectively that Germany had no choice but to resume "unrestricted submarine warfare"?