Microsoft and Sony directly compete in the video-game market, where the PlayStation 4 has a commanding lead over the Xbox One in hardware sales numbers.

Since last year, Microsoft has been pushing the concept of "cross platform" play: the ability to play games like "Minecraft," "Fortnite," and more with friends on PC, smartphone, and even Nintendo's Switch.

Sony refuses to allow games on the PlayStation 4 to work with games on Microsoft's Xbox One and the Switch.

Both video-game fans and game makers are publicly pushing back on Sony's stance — and now the publisher of "The Elder Scrolls: Legends," Bethesda Softworks, has issued an ultimatum.

The massive video-game publisher Bethesda Softworks — the company behind franchises like "Fallout," "The Elder Scrolls," and "DOOM" — just issued a major ultimatum to Sony.

The issue at hand is seemingly simple: Bethesda has a game coming to the Xbox One, the PlayStation 4, and the Nintendo Switch called "The Elder Scrolls: Legends." Bethesda wants "Legends" players on all consoles to be able to play the game with each other and for their progress to carry over if they change platforms.

"The Elder Scrolls: Legends" is a competitive card game, similar to Blizzard's "Hearthstone," that's the same across all platforms, visually and gameplay-wise, whether you're playing it on an iPhone or a PC. The game is turn-based, so it doesn't require precise, reaction-based controls.

In so many words: There's no technical reason it couldn't work across competing platforms like the Xbox One and the PlayStation 4.

"The way the game works right now on Apple, Google, Steam, and Bethesda.net, it doesn't matter where you buy your stuff — if you play it on another platform, that stuff is there," Pete Hines, a Bethesda senior vice president, said in a recent interview with Game Informer. "It doesn't matter what platform you play on — you play against everyone else who is playing at that moment."

Sony, however, won't allow publishers like Bethesda Softworks to enable this type of functionality in their games.

Even Epic Games, the publisher of "Fortnite," isn't allowed to enable cross-platform play between Sony's PlayStation 4 and Microsoft's Xbox One (let alone Nintendo's Switch).

If the biggest game in the world isn't getting around Sony's blockade, how will "The Elder Scrolls: Legends"? Potentially by skipping the PlayStation 4 altogether.

"It is our intention in order for the game to come out, it has to be those things on any system," Hines told Game Informer. "We cannot have a game that works one way across everywhere else except for on this one thing."

By saying as much, Hines and Bethesda drew a line in the sand with Sony's cross-platform policy: Allow cross-platform play and progress, or we'll skip the PS4.

It's a small move in the short term, but it's part of a growing wave of backlash to a long-held policy in the video-game business.

It all started with 'Minecraft'

The Microsoft-owned blockbuster is available on pretty much everything that plays games, from consoles to phones to handhelds.

Microsoft, which makes the Xbox One and directly competes with Sony's PlayStation 4 and Nintendo's Switch, publishes "Minecraft" on Sony and Nintendo (and Apple and Google) platforms in addition to its own Xbox consoles.

More importantly, even though Microsoft owns "Minecraft," the game can be played across competing devices. "Minecraft" players on Xbox One can join up with players on iPhone, Switch, Android, and PC/Mac — even if you're playing in a virtual-reality headset! But Xbox One can't play with PlayStation 4 and vice versa.

Nintendo characters even appear in the Microsoft-owned "Minecraft." Nintendo

That same situation applies to "Fortnite," which launched on Nintendo Switch earlier this summer. Xbox One players can play with those on iPhone/iPad, Nintendo Switch, PC, and Mac — but not PlayStation 4.

Worse: If you're a PlayStation 4 "Fortnite" player, your "Fortnite" account is locked to the PlayStation 4 platform.

Any stuff you've unlocked, and the Battle Pass you paid for? None of that shows up on other platforms if you unlocked it on a PlayStation 4, even though the game uses an Epic Games account separate from your PlayStation Network ID.

That isn't the case for players on other platforms, and it's the latest example of Sony's PlayStation 4 taking a surprisingly exclusionary stance with multiplayer gaming.

When Microsoft announced the "Better Together" update to "Minecraft" — uniting "Minecraft" players across all platforms — it seemed for the first time ever that there was hope that competing game platforms would finally play nice together.

"Sony is a good partner, and they are working with us on this," Matt Booty, the head of Microsoft Studios, told Business Insider in an interview at the time.

In the perfect-world scenario Microsoft was trying to create, "Call of Duty" players on PlayStation 4 could play with "Call of Duty" players on Xbox One, for example — something that's still not the norm even if it makes perfect sense. Why can't "Call of Duty" players on any console play together? Not for a good reason.

It's because Sony and Microsoft are competitors with the PlayStation 4 and Xbox One

But nearly a year later, there's been no movement on the plan to unify multiplayer gaming across the Xbox and PlayStation platforms, despite the number of parties wanting it to happen. That's what the Xbox lead Phil Spencer told Business Insider in an interview in June at the annual E3 video-game trade show in Los Angeles.

"It's impossible to answer this question without saying the name of a competitor," Spencer said, referring to Sony's PlayStation 4. "And as soon as I do that — I don't want to throw stones at anybody."

Instead of speaking to Microsoft's and Sony's respective consoles, Spencer offered an example:

"Say you're not into gaming, and it's your kid's birthday. You buy them a console. I buy my kid a console. We happen to buy consoles of different colors — you bought the blue one, I bought the green one. Now those kids want to play a game together and they can't because their parents bought different consoles. "I don't know who that helps. It doesn't help the developer. The developer just wants more people to play their game. It doesn't help the player. The players just want to play with their friends who also play games on the console. So, I just get stuck in who this is helping."

When asked directly whether there had been any progress, Spencer offered only: "No, no."

But with publishers like Bethesda pushing back on Sony's policy in such a direct way, perhaps progress can begin again.

Competing home video-game consoles haven't been able to play with each other going back to the days of Nintendo versus Sega, but that makes less sense as they've become more alike. The current Xbox One and PlayStation 4 are very similar consoles capable of very similar results (though the PS4 outsells the Xbox One). They even offer similar services, and the world's biggest games are identical on both — look no further than "Minecraft" and "Fortnite" to see that.

And that's before we start talking about smartphones, which are increasingly capable of running the same games that home game consoles can.

"The Elder Scrolls: Legends" is just the latest example of the entire gaming medium becoming more accessible across devices.

Whether you're on a phone or a home game console, you're playing the same game. You play against people on other platforms, and your progress carries over from your phone to your home console or PC.

"There's no, 'oh, it's easier to control, or it has a better framerate on this system,'" Hines told Game Informer. "It's a strategy card game. It doesn't matter."

There's a sense of inevitability to the concept of cross-platform play and progress tracking, as Sony continues to look like the bad guy for keeping the PS4 siloed off, and as even third-party game publishers publicly push back. The company has made only a few statements on the matter, most recently saying, "We're hearing it."

Sony representatives didn't respond to a request for comment on this story.