Google’s parent company Alphabet has sold robotics firm Boston Dynamics to Japan’s Softbank for an undisclosed sum, over a year after putting it up for sale.

As part of the deal, Softbank also purchased Schaft, a lesser known Alphabet robotics subsidiary.

Boston Dynamics is best known for its “BigDog” line of quadrupedal robots, first developed to serve as artificial pack animals as part of a military contract with America’s Darpa research agency.

The robots, alongside the humanoid “Atlas” machine and wheeled hybrid “Handle”, have become viral sensations online, thanks to their eerily lifelike movements, unnerving high-pitched motor sounds and the videos themselves, which feature Boston Dynamics staff torturing their creations with pushes, kicks, shoves and heavy weights to demonstrate their versatility and reliability.

But the firm, which was acquired by Google in 2013, has also failed to fit in with the wider corporate culture of its parent company. Alphabet has a generalised rule against taking military contracts, and while Boston Dynamics was allowed to run out the existing deals it had made with the US military, it has struggled to find a civilian client for its creations. Even its military connections have failed to bear fruit: the US Marine Corps rejected the BigDog robot in 2015, due to the machine’s noise, which would give away troop positions if used in an actual combat situation.

The company was acquired as part of a hiring spree by Android co-creator Andy Rubin, who moved from Google’s smartphone business to head up a new initiative at the company, code-named Replicant, which was intended to bring Google a lead in the robotics space. Within a year of the acquisition, however, Rubin had quit Google to start smartphone company Essential, leading Replicant leaderless and rudderless and Boston Dynamics with little pressure to integrate with its new corporate parent.

It continued to operate from its headquarters just outside Boston, Massachusetts, far from Google’s home in Silicon Valley. In November 2015, according to Bloomberg News, tensions accidentally burst into the open, when the minutes of a terse meeting were published to a company-wide forum. Replicant’s new leader, Jonathan Rosenberg, had told Boston Dynamics that “we as a startup of our size cannot spend 30-plus % of our resources on things that take 10 years,” adding, “there’s some timeframe that we need to be generating an amount of revenue that covers expenses and (that) needs to be a few years”.

Boston Dynamic’s founder, Marc Raibert, had replied, “I firmly believe the only way to get to a product is through the work we are doing in Boston. [I] don’t think we are the pie-in-the-sky guys as much as everyone thinks we are.” A month later, Replicant was folded into Google’s moonshot division, X, but Boston Dynamics wasn’t, leaving the company isolated internally. It was then that Google decided to put it up for sale, but it has taken more than 18 months for a willing buyer to come forward.

Softbank has been on an acquisition spree recently, most notably buying British chip designer ARM Holdings, the company behind most mobile phone processors on the market today, for £24bn. The company has also been pushing its own robotics labs, with creations such as the humanoid assistant Pepper, a $1,600 bot promoted as as world’s first robot with emotions.

It is not clear, yet, whether the acquisition will see Boston Dynamics incorporated into Softbank itself, or left largely independent as part of Vision Fund, the company’s $93bn technology investment fund, as Bloomberg News suggests. Softbank’s shares rose 7.4% in Tokyo on news of the acquisition, although some of that increase was down to an unrelated jump in the US shares of Chinese retailer Alibaba, in which Softbank holds a $105bn stake.

Schaft, the other Google subsidiary acquired in the deal, is a Japanese firm best known for its bipedal S-One robot, which won the Darpa Robotics Challenge Trials in 2014 before being acquired as part of the Replicant build-out. It has operated in extreme stealth mode ever since the purchase, with even its website displaying nothing but an error message.