As mentioned yesterday there's only one of these (or maybe two), and it occurred in 1856. The picture shows the monument to it in Parque Nacional in San Jose.
The War, such as it was, arose because of the Costa Rican President's concerns about the activities of William Walker, an "adventurer" from the USA who had made himself President of Nicaragua.
Walker - prior to the American Civil War according to Wikipedia - "enjoyed great popularity in the southern and western United States, where he was known as "General Walker" and as the "grey-eyed man of destiny."". He attempted to introduce slavery into several Central American States and then bring them into the Union to increase the salve owning vote in Senate and Congress. Without wishing to jump to conclusions he sounds like a fairly odious individual (he is finally arrested by the Royal Navy and handed over to the Hondurans who execute him).
Any how, Walker invaded Costa Rica with his force of "Filibusters" and holed up in a hacienda in Santa Rosa, known as La Casona. In a stroke of military genius he didn't post any guards and went to sleep.
President Mora of Costa Rica had raised an army that was given rifles but left them behind in favour of the machete (which most Costa Ricans seem to have lying around). Wikipedia & my travel guide says he has 9,000 men, our guide said 2,500. As he was a nice man and he lives there, I believe him.
On arriving at the hacienda Mora surrounded the building and called for a volunteer to set fire to the thatched roof. A young drummer boy called Juan Santamaria volunteered, succeeded in the act but died in the attempt. He is one of Costa Rica's few national heroes, and the airport is named after him.
The Americans fled after an engagement lasting 14 minutes. Depending on what you read (and this comes from Wikipedia) Mora followed up and defeated Walker again. Or Walker counter-attacked and got beaten. In 14 minutes. Again. Or it's the same battle described twice and there's 3,000 men involved.
What do you expect from a country that doesn't have an army now, combined with the academic standards the apply in Wikipedia?
Anyway, all a bit confusing and fertile ground for some completely off the wall campaign type game. The game would probably take longer than 14 minutes tho'.