When Grover is talking to Ares at the diner, he mentions the Turbot War, the Lobster War and the 335 Years' War, much to Ares' admiration. These are what is called as "bloodless conflicts": The Turbot and Lobster wars were fishing disputes over said resources, that never started actual wars but led to continuous hostility among countries (Spain and Canada, in one case, and Brasil and France, in the other). The 335 Years' War was a declared war between the Netherlands and the Scilly Island over pirates that did not escalate to a full blown war, but only ended when both countries realized that the "peace" was never declared officially. This is very in keeping with Riordan's faithful recreation of the Greek myths and Ares' depictions in them, in which he was not only the god of war, but of violence, conflict and hostility in general. This further reinforced with Ares starting twitter fights.