Austria declared war on Serbia in a calculated response to the murder of Archduke Franz Ferdinand. There was much blame on both sides as to why war came about and what the true cause was, but the murder was the reason used.
The declaration of independence
The Barbary pirates were seizing US ships for ransom. One time with two British frigates near bye. That forced a change in Jefferson and he realized he had to have a Navy. He order the Constitution class frigates and some smaller vessels. The start of the blue-water Navy.