The banner on Nokia’s website says it all, “Nokia+Microsoft. Here We Go! 11.2.11.” An open letter from Nokia CEO Stephen Elop, and Microsoft CEO Steve Ballmer revealed today that Nokia and Microsoft will develop a long term partnership.

“Today in London, our two companies announced plans for a broad strategic partnership that combines the respective strengths of our companies and builds a new global mobile ecosystem. The partnership increases our scale, which will result in significant benefits for consumers, developers, mobile operators and businesses around the world. We both are incredibly excited about the journey we are on together,” the letter said.

Microsoft’s Bing will be used to power searches on Nokia smartphones, and Windows 7 phone will become the main operating system, sidelining Symbian which will become “a franchise platform.” The company is still expecting to sell 150 million more Symbian devices in the future, according to BBC News.

“It is a transition from Symbian to Windows phone as our primary smartphone platform,” said Elop.”We reserve the right to introduce tablets using other platforms, including ones we may be working on internally,” he added.

According to the open letter from Nokia and Microsoft, there will be other changes that will take place. It is expected that Microsoft AdCenter will provide search advertising services for Nokia smartphones. Nokia’s content and application store will be integrated with Microsoft Marketplace, and Nokia Maps will become a “core part” of Microsoft’s mapping services. Nokia and Microsoft will also work on joint marketing services, and shared development goals.

As for location, Nokia doesn’t intend to move, and that it is first and foremost a “Finnish company.” Elop also announced that he expects “thousands” of job losses in Finland, as a result of this partnership, reports Reuters.

The Joint letter also says that the battle is no longer a battle of mobile devices, but of mobile ecosystems, and the two companies share similar goals and their “strengths are complimentary.” Nokia and Microsoft vow that “There are other mobile ecosystems. We will disrupt them. There will be challenges. We will overcome them. Success requires speed. We will be swift.”