This is perhaps the only formal war where one of the belligerents was not human, but rather avian.
In 1932, the emu population in Australia was growing out of control, with an estimated 20,000 emus running around the Australian desert and causing havoc among crops.
In response, the Australian military sent out a task force of soldiers armed with machine guns to kill the emus and even jokingly declared war on them.
In mid-November they drove out into the desert and proceeded to hunt down any emus they could find.
However, they ran into complications; the emus proved remarkably resilient, even when struck by multiple machine gun bullets they continued to run away, easily outstripping the heavily laden soldiers.
The Emu War lasted for nearly a week before Major Meredith, the commander of the emu-killing task-force gave up in disgust after the soldiers only bagged a fraction of the elusive birds.
War duration: (November 11-18 1932) Seven days.
Casualties: 2,500 emus.