And reusing assets in future titles will help 'optimise the investment', CEO says.
Hollywood high flyers Adam Cooper and Bill Collageare brought on by New Regency.
Around 2 million units below Assassin's Creed 3 in the same time frame.
Alleged ex-dev talks 'troubled' development of 2012 Assassin's Creed.
Also Stealth Inc, New Little King's Story and Urban Trial Freestyle.
The PS3 exclusive becomes the first title of 2013 to hold the No.1 spot for four consecutive weeks.
"We want to be prudent on our expectations," says Ubisoft boss as Assassin's Creed 3 ships 12.5 million.
Available today for Xbox 360, tomorrow on PC and PS3, says Ubisoft.
Also pre-order BioShock Infinite ahead of its March 26 release.