Tony Pulis has called for unity at West Brom after he was confirmed as the Baggies' new head coach.
The former Crystal Palace and Stoke boss has signed a two-and-a-half year contract at the Hawthorns to replace the sacked Alan Irvine.
The Albion board have outlined survival in the Barclays Premier League is Pulis' priority.
They were 16th and a point above the relegation zone ahead of the New Year's Day trip to West Ham.
Pulis will watch from the stands at Upton Park before taking charge for Saturday's FA Cup third-round tie with Gateshead.
Fans turned on Irvine at the end of his six-month reign and Pulis has issued a rallying cry.
He said: "I'm absolutely delighted to accept the job and I do so with a simple but important message for the Albion fans and everyone at the club.
"Every successful club is built on unity and that is what I shall strive to help bring to Albion. We need everyone together from top to bottom - the supporters, all the staff, the players, everyone who has an interest in the club's welfare.
"With that, we can go forward together and hopefully take this club up the Premier League."
Pulis left Crystal Palace in August, reportedly following a dispute over transfer policy, after saving them from relegation last season. He guided the Eagles to 11th and won the Barclays Premier League Manager of the Year award for 2013-14.
He beat Tim Sherwood to the job with the former Tottenham boss losing out on the role for a second time after Irvine was picked ahead of him in June.
Irvine was sacked on Monday after just four wins in 19 league games and seven defeats from the last nine outings.
Pulis will work within the current Albion set-up alongside technical director Terry Burton.
"We are delighted to secure a man of Tony's calibre and proven ability," Burton said.
"He made it clear this position excited him and he was eager to get back into the business of winning Premier League points - and there are few who know how to do it better."
- More about:
- West Bromwich Albion