Question

Imagine you are an advisor for a sitting US president. You have just received word that three small boats appear to have attacked a US port. The president wants to retaliate, but you think more evidence is needed before US forces attack. What historical event could you reference to support your case best?

Answer 1

An historical reference that could as function as a reference is the Cuban Missile Crisis in 1961.

When the soviet missiles were transported by sea and arrived to Cuban soil, they could be shot from there and they would reach US territory (Florida).

This was understood as a direct threat to the US. It the US had decided to retaliate in that moment by sending a direct attack, the Cold War conflict would have been transformed into a direct conflict between two blocs that owned nuclear weapons, so it had probably led to the world's destruction. Fortunately, although the tensions were really high, the US decided to wait and negociate instead of sending an attack in the first hand.  

Answer 2

The best piece of historical evidence you could use to justify a counter attack in a situation like this would be the bombing of the USS Cole, which greatly changed the rules of engagement.