Earlier in the year, the US Air Force had announced that it expects to complete its transition to Microsoft's latest Windows operating system by March 31. It was also revealed that the Department of Defense was pushing to decommission systems not updated to Windows 10 by that deadline. It now appears that the DoD has managed to migrate nearly all of its offices to Windows 10.

In a years-long process that also involved replacing a huge number of existing machines because they were not compatible with Windows 10, the Pentagon appears to be finally done with the transition.

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"For the most part, with the exception of a couple [of agencies], we are there," Essye Miller, the Acting Department of Defense Chief Information Officer (DoD CIO), announced during an industry day in National Harbor, MD.

"We'll spend sometime this morning with the deputy secretary just congratulating folks for their hard work," she added. "It's been a long, long, long journey."

The DoD had initially set a January 2017 deadline, which was missed. Then the Department gave all of its agencies the deadline of March 31, 2018 to complete migrating their systems to Windows 10. At the time, it had said that Windows 10 "security features allow software patches to install faster, making it less obtrusive to Airmen while its ability to counter emerging cyber intrusion makes the networks safer."

Since the release of Windows 10 in 2015, Microsoft has used the support from the Department of Defense as the operating system's biggest selling point for the enterprise market. "One of the largest enterprises anywhere – the US Department of Defense (DoD) - has joined the ranks of enterprise customers planning swift Windows 10 deployments," Microsoft had said back in 2016.

The statements from the DoD and its agencies were used to boost user confidence in the first ever Windows as a Service release that attracted quite a few controversies over data collection and privacy concerns. Microsoft recently announced reorganizing its Windows team and also revealed that nearly 700 million active machines are powered by Windows 10.

"This will have a positive security impact on the protection of DoD and special access programs, mission systems, as well as strategic, tactical, and research, development, testing and evaluation systems," the DoD had said earlier this year.