Fifteen months after its debut, Windows Phone is heading to China, the most heavily populated country on Earth. Microsoft announced this morning that the first Windows Phone handset aimed at the Chinese market is now available in that country, with more to follow in the weeks and months ahead.

"To mark the arrival of Windows Phone, Microsoft China held an event in Beijing for press and phone industry executives Wednesday to show off the Chinese-language interface," Microsoft's Michael Stroh wrote in the Windows Phone Blog. "Many great Windows Phone handsets are headed for China from Nokia and other phone makers this year, so stay tuned."

The first to arrive, however, is the HTC Eternity, an unlocked handset with a 4.7" screen, front- and rear-facing cameras, and the latest Windows Phone software update, the awkwardly named Windows Phone 7.5 Refresh (formerly "Tango"). The Eternity is also "stocked with a slew of popular Chinese apps," Microsoft says.

Microsoft created the Windows Phone 7.5 Refresh specifically to move its high-end smartphone platform into the low end of the market. As such, it works on devices with far less RAM than most Windows Phone handsets and it consumes less system resources in use. But Microsoft says that this new Windows Phone OS is compatible with the vast majority of software that's currently available. And the company is working with developers to change the apps that won't work.

Bringing Windows Phone to China is a lot more complex than lowering equipment prices, however. The software had to be localized for Chinese and certain services that are integrated with the Windows Phone OS—like Facebook and Twitter—are banned in that country. So Microsoft modified the OS further to work with China-based services.

The Chinese market is considered a key area of growth for smartphones in 2012, and hardware makers are expected to sell nearly 140 million handsets there this year, more than in the United States.

Nokia, LG, and ZTE are among the other companies known to be prepping Windows Phone handsets for the Chinese market. Nokia's Windows Phone 7.5 Refresh-based device, the Lumia 610, will ship in the second quarter and cost less the $180 (US). The iPhone 4S costs five times that amount in China. Analysts expect Windows Phone sales in China to exceed those of the iPhone by 2016.