Microsoft today released Halo: Spartan Assault for Windows 8 and Windows Phone 8, but there’s a bit of a catch. The Windows Phone version in the US will be a Verizon exclusive for the first month.

An official blog post described the game as “available worldwide except in the U.S., where Verizon Wireless customers get first dibs until August 16.” Microsoft is of course free to make its own business decisions, but the Verizon exclusive strikes me as an odd choice as it’s bound to engender ill will among Windows fans on AT&T and T-Mobile.

This is a big launch for Windows Phone 8, as it represents the first time that Microsoft’s Halo franchise has landed on mobile devices, but a whole swath of US customers won’t be able to take advantage. For instance, when Nokia launches its flagship 41-megapixel Lumia 1020 smartphone on AT&T next week, early adopters will have to wait three weeks before they can play the game.

Another mild point of friction with the launch is Microsoft’s effort to promote the game as working with saved states across devices, allowing users to start playing on a phone and then pick up where they left off on a PC or Windows tablet. Except, of course, that you’ll have to buy the same game twice. At $6.99, the game’s pricing is reasonable, but Microsoft isn’t always being clear about the need for two different licenses, such as in this post.

Microsoft is in the midst of a transition to eliminate these kinds of situations. The company recently announced a new “One Microsoft” strategy that will consolidate the firm’s multiple OS teams under one division head. For what it’s worth, Microsoft isn’t the only one with this problem. For instance, users buying games and apps on iOS still have to buy Mac App Store versions if they want them to work between Macs and iPhones.

In addition to driving Windows Phone, Halo: Spartan Assault is meant to showcase Microsoft’s own Surface hardware. At a press briefing ahead of the game’s official announcement in June, the company was showcasing an early version of the game on the Surface Pro.

A casual-gaming Halo title isn’t likely to have a huge impact on Surface sales, but, at this point, Microsoft could use any help it can get. The firm just took a $900 million inventory charge on the Surface RT after having to slash prices to move units. No matter how you calculate it, that’s still a lot of tablets that need buying.

Halo: Spartan Assault does look great, and its control scheme is workable, although a bit awkward. If you aren’t an AT&T Windows Phone 8 customer, it’s a solid purchase. But if you are, you’ll just have to wait.

Image credit: Microsoft