Carthago delenda est.

That's the phrase Facebook CEO Mark Zuckerberg drilled into his employees' heads in June 2011 after the launch of Google+, Google's wannabe Facebook killer.

It was a phrase that was used millennia ago by Cato the Elder, a Roman senator who was known for his intense antipathy toward Carthage, the empire that aspired to destroy and conquer Rome. Cato used it to end each of his speeches. After the arrival of Google+, Zuckerberg gathered his employees in a room and made the phrase his own.

"You know, one of my favorite Roman orators ended every speech with the phrase Carthago delenda est--Carthage must be destroyed," Zuckerberg told his employees that day, according to book Chaos Monkeys. "For some reason, I think of that now."

Faced with a threat to his company's very existence, Zuckerberg inspired his team to work harder and longer than their rivals in Mountain View. Facebook copied any and every feature of value from Google+, stripping it like a car left overnight in the wrong part of town. Technically, Google+ still exists, but really, the service has been dead for many years. Carthage has been destroyed.

Now Carthage is Snapchat.

Zuckerberg made as much clear Tuesday at F8, Facebook's annual developer conference. Rather than celebrate the event's 10th anniversary or the growth of Facebook, Instagram, or Oculus, Zuckerberg focused the key opening minutes of F8 on his company's chief rival.

Of course, Zuckerberg did not call out Snapchat by name. Rather, he did it by putting the spotlight on Facebook Camera, its clone of Snapchat's key feature.

Zuckerberg's battle with Snap has been in the works for years, at least since his offer to purchase the upstart company for $3 billion in 2013 was promptly rejected by Snap CEO Evan Spiegel.

Since then, Facebook has tried on numerous occasions to do away with its Snap problem by simply copying the app. It tried this in 2012 with Poke and then again in 2014 with Slingshot, two embarrassing app failures. Zuckerberg finally began to get serious about his Snap problem in August when Instagram rolled out a clone of Snapchat's defining feature: Story.

Snapchat Stories allow smartphones users to share the goings-on in their lives to their friends through photos and videos. Whereas one would previously broadcast their lives via text-based status updates on Facebook, they now do so using videos Stories on Snapchat.

This is why Story features now exist not just on Instagram but also on WhatsApp, Messenger, and even the main Facebook app. Facebook is clearly at war with Snapchat. And some observers think the outcome is so certain, Spiegel would be wise to cut his losses and find a buyer now.

"Photos and videos are becoming more central to how we share than text," Zuckerberg said just one minute into his keynote on Tuesday. "So the camera needs to be more central than the text box in all of our apps."

A few minutes later, Zuckerberg made the signature announcement of F8 2017: the Facebook Camera Effects Platform. With this platform, Facebook is calling on its community of developers to use its Snapchat clone technology to create an array of augmented reality, camera-first experiences. (Snapchat, meanwhile, sought to steal a march on Facebook with an announcement of its own Tuesday, revealing World Lenses, augmented-reality filters that let users place virtual 3-D objects in their photos.)

With a tool called Frame Studio, artists and designers will be able to create geography-based photo frames. ARStudio, meanwhile, is a tool that allows developers to create 3-D augmented reality animations and effects, such as a video game-like helmets that stick to users faces. These developer tools are rolling out now, but already, notable developers have put them to use. Throughout the keynote, Facebook displayed third-party developed camera experiences created by the likes of Nike, Electronic Arts, and Giphy.

"This is going to be a really important technology that changes how we use our phones," Zuckerberg said. "Even if we were a little slow to add cameras to all of our apps, I'm confident that now we're going to push this augmented reality platform."

If Zuckerberg called on his employees to resist and defeat the threat of Google+, he is now calling on all of Facebook's partners to squash the new upstart.

Snap must be destroyed.