Charlie Bell, one of the architects of Amazon Web Services, is heading to Microsoft, according to multiple media reports. An internal memo in early August announced Bell was leaving Inc. after 23 years. He most recently served as senior vice president of AWS and was a member of the company’s senior leadership team, or S-Team, that surrounds the CEO.

The move could mark another shot fired in the cloud wars between the two companies. Microsoft and Amazon have fought over cloud contracts, with the former gaining ground as a serious competitor, though there hasn’t been a defection between the companies’ cloud divisions of this level before.

Bell is one of the most high-profile executives to leave the company over the past year. Founder Jeff Bezos shocked the world when he announced he was stepping down as CEO, but he’s still with Amazon and holds his spot as chairman of the board of directors. Bell had been expected to fall into a new role with the CEO shakeup — former AWS CEO Andy Jassy took over for Bezos — but former Tableau CEO Adam Selipsky was lured back to Amazon to take over for Jassy.

Several executives have left Amazon over the past couple years, including longtime leaders of the company’s most important divisions. Jeff Wilke, former CEO of Amazon’s retail division, left in early 2021. Former Senior Vice President Steve Kessel, who led Amazon’s physical retail development, announced his retirement in 2019. And as Amazon opens up more Fresh stores, its grocery Vice President Wei Gao announced she was leaving the company.