Costa Rica had a fair sized and trained army in the late XIX Century because the isthmus was the target for filibusters coming from the South of the USA. Costa Rica was invaded in 1856 by a group of filibuster that consisted of men from USA, England, France and Prussia but were defeated at the Battle of Santa Rosa on March 20th, 1856. After this combat our goverment formed an Expeditionary Force that went to Nicaragua to try to finish with the filibusters (they took control of Nicaragua by then) and the following battle, Rivas, was an unconclusive bloodshed in which Costa Rica lost, in some 10 hours some 1,000 soldiers and was saved in the last minute by a reserve batallion returning from a patrol. After the battle a cholera plague came killing, at least, 30% of the population of Nicaragua and Costa Rica. When the plague was over both contendants, filibusters and Costa Ricans, took until 1857 to re engage in military operations, this time over the control of the San Juan river and the Caribbean port of San Juan del Norte. Those operations went better for Costa Rica than those of the previous year and the filibusters were finally cornered when units from Guatemala, Salvador and Honduras came to help. However the filibuster leader, William Walker, surrendered to a US Navy frigate captain who took him to the US under the promise of never doing such an act. But Walker insisted a year later but this time the central american allies act faster and arrest him and, without any trial, he was shot dead. After that war several internal factious wars took place in Costa Rica ending in the greatest battle fought in Costa Rican soil in "La Angostura" where the goverment won and shot the survivors that came from El Salvador leaded by an ex President and his former CiC, General Cañas.
But with time and lack of a real menace the institution came into a coma. By 1917 there was a coup in which the army was barely involved and the situation was fixed without bloddshed (except from the guy that made the coup who was properly assesinated).
During the 30ies and WWII Costa Rica played along FDR and we got some equipment which included some P 51 and such. But by then a communist oriented President decided that his candidate must win the 1948 elections at all costs, even against the result at the polls and a civil war broke. The result of the civil war was the deposition of the President and exile and a Revolutionary Junta took control and call the people to the polls for a new constitution. One of the points, then, was if Costa Rica needed or not an army. Because in Latin America armies are not for figthing wars against foreign powers but to use them as instruments of the oligarcs to kept the people under their heels then we decided that the army must be eliminated as an institution. So, no army.
In case of emergencies, as in the 80ies when the comunist regime of Nicaragua was trying to infiltrate our country the goverment called to the "Reserve" which is like the US "weekend warriors" (I was then a volunteer and expend my time training and at the border) which was quite big and strong thanks to the help of US hero president Ronald Reagan. Friendly countries sent Camberra fighter planes, Galil assault rifles and any kind of help. In 1986 USS Iowa itself came to our shores where it fired it´s main guns showing some fire power to the commie rats which, at the end, never produced their full scale invasion.
Since then the "Reserva" has never been called again. Some units have been activated for specific natural disasters but that´s all.
Now we are living quite a situation because without appropiate armed forces then our territory have been vulnerable for international drug dealers and criminal gangs. It has been quite an important topic for the upcoming elections and the "socialists" still call for "social programs" to fix the criminal problem and the oposition (specially the right wing) are calling for aditional money, men and weapondry to deal with this challenge.
Basically that a summary of the military history in Costa Rica.
An appeaser is one who feeds a crocodile, hoping it will eat him last.
Sir Winston Churchill