World War I Britain supplies cut?
I was watching a documentary regarding World War I and one of the things that was depicted was how the commercial trade was cut off from Germany by England blocking the sea which resulted in Germany being brought close to starvation, same thing happened when Germany started attacking Commercial boats on its way to England to deliver supplies, provisions and raw materials, until the US joined the conflict and helped them to avoid being brought to starvation. My question here is, weren’t Germany and Britain self maintaining countries and economies already before World War I? What were they doing before war to provide for its people? Was all their provisions coming from the USA and other countries? Where they so reliant on other countries to basically survive? Will appreciate if anyone has insight on this. Thanks!