Arsenal manager Arsene Wenger made a triple swoop for Fenerbahce defender Andre Santos, Werder Bremen centre-back Per Mertesacker and Chelsea midfielder Yossi Benayoun on transfer deadline day.
Brazilian full-back Santos and Germany international Mertesacker arrived as Wenger bolstered his defence following the Gunners' 8-2 thrashing by English champions Manchester United last weekend.
Both players have signed long-term contracts, with Santos believed to have cost £6.2 million ($10 million) and Mertesacker joining for a reported fee of £8 million ($12.9 million).
Israel international Benayoun joined on loan for the rest of the season after the former Liverpool star was told he could leave Chelsea and he will be expected to fill the creative void left by Samir Nasri's recent departure to Manchester City.
Benayoun, who is currently on international duty, wrote on micro-blogging website Twitter: "I sign with Arsenal, very happy and excited about it, but now my head is only in the game against Greece on Friday, thanks for the support."
Santos, 28, helped Fenerbahce win last season's Turkish title but did not feature in Brazil's 2010 World Cup squad.
"Santos is a quality player, with the ability to both defend well and get forward and help with attacks," Wenger told Arsenal's website.
"He has experience in the Champions League and for Brazil and has proven he can deliver at the highest level.
"We welcome Santos to the club and look forward to him having a big impact for us."
Santos becomes the latest Brazilian to head to Arsenal, following compatriots Denilson, Sylvinho, Edu and Gilberto Silva.
"It was one of my dreams to play for a major European football club and I have accomplished this. I am very happy to be part of this team," Santos said.
"All the Brazilians who came to this club spoke wonders about it and I am delighted to be part of the Arsenal family."
In 75 games for Germany, Mertesacker has helped his country to the Semi-Finals of the 2006 and 2010 World Cups and to the Final of the 2008 European Championship.
Wenger believes the 6ft 6in defender should add some steel to a notoriously error-prone Arsenal rearguard and he said "He is a German international with vast experience and strength and is good on the floor and in the air.
"I believe he will be well-suited to the Premier League and a tremendous asset to the team."
Mertesacker added: "Moving to London enables me to fulfil a dream and a further step in my career. The Premier League has always represented a great challenge for me."
Wenger has been active in the final few days of the transfer window, signing South Korea captain Park Chu-Young from Monaco, the club where the Frenchman made his name as a manager, on Tuesday.