West Ham boss Alan Pardew has completed a triple swoop for Cardiff centre-back pair Danny Gabbidon and James Collins and Charlton full-back Paul Konchesky.
Gabbidon, 25, Collins, 21 and Konchesky, 24, have signed long-term contracts at the Upton Park club.
The total fee for the trio is thought to be around £4.5m - and may rise depending on clauses and appearances.
"Danny can compete at the highest level, James is an excellent prospect and Paul's a top player," Pardew said.
Pardew added: "With the signing of James and Danny we now have five of the best young centre-backs in the country.
"Danny comes to West Ham United with a lot of experience for a player of his age.
"At just 25 years old he is already a key player for the Welsh national team and has shown a lot of maturity in his performances.
"Pace and agility will be his major assets as Danny makes the transition to the Premier League.
"James is probably lacking experience as he joins the club, but do not underestimate his potential."
The moves leave new Cardiff boss Dave Jones with a huge hole in his defence, but goes some way towards his task of cutting the cash-strapped Bluebirds' wage bill by a third.
"Clearly sacrifices have to be made and this is a summer of sacrifices", Cardiff City owner Sam Hammam said.
As well as lowering the wage bill, Hammam said the club needed to raise a minimum of £2.5m.
Konchesky has made 168 appearances for Charlton and Pardew is delighted to have captured a player with so much Premiership experience.
"He is only 24, but has well over 100 Premier League games to his name and I feel he can only get better from here.
"His great strength is going forward from full-back and that could be a real asset this season."
Konchesky himself added: "This is a real strong group of players - a good blend of youth and experience.
"If we play well as a team, we'll have a great chance of not only surviving in the Premier League, but also taking the club forward over the next few seasons."