A telling confirmation of Ricardo's insight is that, when nations go to war, their first order of business is often to try to block the other's access to trade. In the American Civil War, the North won in large part because its blockade of Southern ports prevented the Confederacy from exporting its cotton.
In the twentieth century, the fact that Great Britain and its allies were able to disrupt German trade more successfully than Germany could impede the flow of goods into and out of Great Britain bore importantly on the ultimate outcomes of both world wars.