Ok. Now your innocent question of "what is guano" has the history major in me looking at stuff. You all drive me crazy because you say something and I just have to know...The Chincha Islands War (Spanish: Guerra hispano-sudamericana) was a series of coastal and naval battles between Spain and its former colonies of Peru and Chile from 1864 to 1866. The conflict began with Spain's seizure of the guano-rich Chincha Islands in one of a series of attempts by Spain, under Isabella II, to reassert its influence over its former South American colonies. The war saw the use of ironclads, including the Spanish ship Numancia, the first ironclad to circumnavigate the world.
So - there have been wars over many things, including bird poop. How apt.