He chose to leave out his regulars in the last international window for friendlies against Ireland and Burkina Faso, using the opportunity to give fringe players the chance to impress ahead of the World Cup finals in Qatar.
But the likes of Thibaut Courtois, Kevin De Bruyne, Romelu Lukaku and Eden Hazard, now recovered from injury, were all named for the matches against the Netherlands, Poland and Wales.
Belgian host their Dutch neighbours in Brussels on June 3 and Poland on June 8 before going to Wales on June 11 and Poland in Warsaw on June 14.
“The last match camp I was trying to see a little less experienced players in that environment, and I thought the experience was really valuable for us to get information. But this is the real competitive camp, we got four games inside 14 days, something that we’ve never done before,” Martinez told a news conference.
“That’s why we need a lot of bodies. Because every day is important for us to work. This is a very experienced group. We’ve been working now for six years, we know each other very, very well. And it’s important that we have time together,” he added.
Forwards Christian Benteke and Divock Origi were left out while Jeremy Doku is being given time to continue his recovery from injury.
Belgium, who recently lost top place in the FIFA rankings, take on Canada, Morocco and Croatia in Group F at the World Cup in November and December.
Goalkeepers: Koen Casteels (VfL Wolfsburg), Thibaut Courtois (Real Madrid), Simon Mignolet (Club Brugge), Matz Sels (Racing Strasbourg)
Defenders: Toby Alderweireld (Al Duhail), Dedryck Boyata (Hertha Berlin), Timothy Castagne (Leicester City), Jason Denayer (Olympique Lyon), Wout Faes, Thomas Foket (both Stade Reims), Brandon Mechele (Club Brugge), Thomas Meunier (Borussia Dortmund), Arthur Theate (Bologna), Jan Vertonghen (Benfica)
Midfielders: Yannick Carrasco (Atletico Madrid), Kevin De Bruyne (Manchester City), Leander Dendoncker (Wolverhampton Wanderers), Thorgan Hazard (Borussia Dortmund), Amadou Onana (Lille), Dennis Praet (Torino), Alexis Saelemaekers (AC Milan), Youri Tielemans (Leicester City), Hans Vanaken (Club Brugge), Axel Witsel (Borussia Dortmund)
Forwards: Michy Batshuayi (Besiktas), Charles De Ketelaere (Club Brugge), Eden Hazard (Real Madrid), Adnan Januzaj (Real Sociedad), Romelu Lukaku (Chelsea), Dries Mertens (Napoli), Lois Openda (Vitesse Arnhem), Leandro Trossard (Brighton and Hove Albion).