Marian Rejewski and Henryk Zygalski hiked over the Pyrenees with a guide (who robbed them at gunpoint) to the Spanish border, where they were arrested on January 30, 1943. They were incarcerated by the Spaniards for three months before being released, upon Red Cross intervention, on 4 May 1943. They then managed, by a circuitous land–sea–air route, to join the Polish Armed Forces in Britain, Rejewski and Zygalski were inducted into the Polish Army as privates (they would eventually be promoted to lieutenant) and put to work breaking German "SS" and "SD" hand ciphers at a Polish signals facility in Boxmoor. Because of their having been in occupied France, the British considered it too risky to invite them to work at Bletchley Park.