The former Bolton, Newcastle and Blackburn manager yesterday agreed a two-year contract to attempt to guide the relegated Hammers back to the Barclays Premier League.
The appointment has divided opinion among the Upton Park faithful, with many supporters turned off by Allardyce's direct style of play.
Owners David Sullivan and David Gold have opted for pragmatism over sentiment, with the 56-year-old having taken Bolton from the Championship into Europe during his spell at the Reebok Stadium.
"I wouldn't have taken this job if I didn't think we could bounce straight back into the Premier League," said Allardyce.
"More than that, I wouldn't have contemplated the job if I didn't think there was the opportunity to build something substantial at West Ham.
"I know there will be West Ham fans asking whether I'm going to abandon the style of play that's been the club's heritage over the years.
"All I'll say is it will be a tale of home and away. At Upton Park we'll try to play the kind of game the fans want. We will aim to continue in the same way on our travels but we'll also be tough, hard to beat and utterly resilient."
Allardyce, who has been out of work since his surprise sacking by Blackburn's new owners in December, has reportedly been offered a huge bonus if the Hammers are promoted next term.
He replaces Avram Grant, who was axed minutes after West Ham's relegation was sealed by a 3-2 defeat at Wigan less than a year into a four-year deal.
But Allardyce is unlikely to be able to prevent an exodus of the club's best players. Goalkeeper Robert Green, striker Carlton Cole and player of the year Scott Parker are all expected to quit Upton Park over the summer. "That's probably going to be the case for financial reasons," Allardyce added. When a club is relegated it's a massive loss of revenue and you have to adjust. But for me, whatever happens, the basis is there of a very good squad and some good young players."
On the future of England midfielder Parker, Allardyce concedes it will be "difficult" to keep him. He said: "I don't know yet, we'll have to wait and see. From a distance it looks very difficult, but there is no indication of any bids for Scott yet."
Allardyce confirmed he has added Neil MacDonald, his assistant at Bolton and Blackburn, to the backroom staff.