It's what's known as a bioluminescent burglar alarm, and just like the alarm on your car or your house, it's meant to cast unwanted attention onto the intruder, thereby either leading to his capture or scaring him away.

Whether this is a personal decision whether you're going to install a burglar alarm in your home or a national decision where you're going to invade some foreign country you're going to trade off something, either money or time, convenience, capabilities, maybe fundamental liberties.