Spies Like Us: Homing Pigeons

So I'm trying something new this week: a theme! Every day this week I'll be writing about something that has to do with spying, spies, Harriet the Spy, etc. Today, we'll be looking at homing pigeons.
The grey birds have played an important part in intelligence work since the beginnings of espionage. While carrying vital secrets, the birds can soar high over enemy lines. In Roman times, Caesar used them to send messages during his campaigns. Ever since, spies have valued the pigeon's speed and its ability to return home in almost any weather. When we think of homing pigeons, we, of course, think of WWI when more than 500,000 birds carried messages back and forth. Reconnaissance pigeons even carried tiny cameras in the sky to take pics of enemy fortifications.
In WWII, spies used pigeons to guide bombers to the launch sites of the German V1 "flying bombs." Meanwhile, soldiers on the front line were ordered to shoot any bird even before they saw the whites of their eyes. Pigeons could carry only light loads, so the messages had to be really small or else reduced to a microdot, which would later be enlarged.
No one really understands completely how the birds are able to make their way back "home." Most researchers believe that they have an inner compass mechanism that relies on the sun. It's also thought that the birds can detect the Earth's magnetic field. Whatever the reason, the homing pigeon is probably (hopefully) a thing of the past. My favorite story about these spies is the one about a specific bird named Cher Ami, who was awarded the French Croix de guerre for his heroic service in delivering 12 important messages during WWI, despite having been very badly injured. Now that's what I call giving "flipping the enemy the bird!"