It’s a Martin invasion: Two musicals about the true medieval mystery of Martin Guerre premiere in two cities in July. Guerre was the Frenchman whose reappearance in 1557 after an eight-year absence made villagers doubt his identity (and inspired 1982’s French film The Return of Martin Guerre and 1993’s Sommersby). At Chicago’s Goodman Theatre, The House of Martin Guerre opened July 1 after development backing from producer Garth Drabinsky (Show Boat); on July 10, Martin Guerre, from producer Cameron Mackintosh and the makers of Les Miz, opens in London. But which show will make it to Broadway, where Mackintosh has four hits? ”Anyone producing [House] in New York without their own theater will need someone to give them one — and nobody wants to antagonize Mackintosh,” says House composer Leslie Arden. A spokesman for Mackintosh said it’s ”the storytelling that counts.” As well as who tells it first.