Microsoft on Tuesday began upgrading Windows 10 PCs running the 14-month old 1803 with the latest refresh, the May 2019 Update, aka 1903.

"We are initiating the Windows 10 May 2019 Update for customers with devices that are at or nearing end of service and have not yet updated their device," Microsoft said on its Windows release health dashboard. "Keeping these devices both supported and receiving monthly updates is critical to device security and ecosystem health."

Windows 10 1803, which was released April 30, 2018, will drop off Microsoft's support list on Nov. 12.

In May, Microsoft announced that the forced upgrade would begin in "late June." It was unclear what delayed the 1803-to-1903 migration.

The move marks the first time Microsoft has started to upgrade Windows 10 Home and Windows 10 Pro personal computers since the April jumble of its update process. Rather than force consumers to accept each feature upgrade on the company's terms - since 2015, Microsoft had decided when each device was told to download and install a refresh - developers added a new "Download and install now" (DaIN) option to 1903, and refitted 1803 and 1809 with it as well.

DaIN lets users choose when to migrate from one version to another. If one does not apply DaIN, the current feature upgrade is not to be automatically downloaded and installed on the PC. The result: Windows 10 Home users could, for the first time, skip a feature upgrade by simply doing nothing. With DaIN, those running 1803 would be able to bypass the troubled 1809 by not choosing the option. (Under prior rules, Windows 10 Home users would have been forced to upgrade to 1809 before later moving to 1903.)

But Microsoft won't let people run a Windows 10 version indefinitely. Citing security, it promised that when the current feature upgrade neared end of support, the company would intervene by downloading the latest and ordering the PC to install it. That intervention is what Microsoft said has now begun.

"Based on the large number of devices running the April 2018 Update, [which] will reach the end of 18 months of service on November 12, 2019, we are starting the update process now for Home and Pro editions to help ensure adequate time for a smooth update process," the health dashboard top-of-page message read.

Although Microsoft did not say how far ahead of end-of-support it planned to kick off force upgrades when it first revealed the DaIN-related changes, it has started the process almost exactly four months before 1803's retirement. That time period seems a minimum, what with the large numbers of PCs still running 1803.