Out of curiosity, I was recently looking up a little information about the South American War of the Triple Alliance. During that little search, I ran across references to an "Operation of Thirty Hours" that involved Brazil nearly going to war against Uruguay in 1971. But just try looking for that on Google. Luckily, I found a good English page about the affair.

The short story is that Uruguay came very close to electing a certain leftist party, and Brazil's dictator at the time didn't like that. There's a good chance the US was involved in getting the dictator to not like that, but it's also possible Brazil's politicians were worried about socialist or communist uprisings, like the one Fidel Castro led in Cuba.

Brazil's military forces were in their vehicles, ready to go (and expecting to control the country in a whopping thirty hours, hence the name of the operation), when the leftist government lost the election. Kind of like a war where nobody came.