What happened

Shares of General Motors (NYSE:GM) popped a good 5.3% in early trading Wednesday. They've since settled down to enjoy a more modest 2.6% gain (as of 12:20 p.m. EDT). That doesn't detract from the magnitude of today's news, however:

Honda Motor Company (NYSE:HMC) is investing $2.75 billion in GM!

Robot driving in a cockpit

Robot taxis may be coming soon -- courtesy of Honda and GM. Image source: Getty Images.

So what

The companies announced the venture Wednesday. Honda will initially invest $750 million in General Motors' Cruise autonomous vehicle (AV) division, followed by investments totaling at least $2 billion over the next 12 years.

Together, the two companies will proceed to "work jointly" to "develop a purpose-built autonomous vehicle for Cruise that can serve a wide variety of use cases and be manufactured at high volume for global deployment."

Now what

For investors who've assumed that General Motors' decision to buy Cruise two years ago was as a way to acquire software to install in its Chevrolet Bolt in order to facilitate sales of a GM-built vehicle, this announcement has to come as a surprise. But as GM CEO Mary Barra explained, this is actually "the logical next step in General Motors and Honda's relationship, given our joint work on electric vehicles, and our close integration with Cruise. Together, we can provide Cruise with the world's best design, engineering and manufacturing expertise, and global reach to establish them as the leader in autonomous vehicle technology -- while they move to deploy self-driving vehicles at scale."

Whether that means that Cruise will now aim to build its software into a Honda-built car, a GM-built car, both, or some other combination of the two, remains to be seen. One thing is clear, however: With GM and Honda teaming up to create an alliance that sells 15 million cars a year worldwide, the competitive landscape just shifted.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.