ɪt wʌzɐ sˈuːpɚɹɛŋkɹˌɪptᵻd kˈoʊd, ᵻvˈɛntʃuːəli ɐ tˈuːbˈʊk sˈɪstəm, ænd dʒˈɔɪnt kɹɪptˌænɐlˈɪɾɪk pɹˈɑːɡɹɛs wʌz slˈoʊ.
It was a superencrypted code, eventually a two-book system, and joint cryptanalytic progress was slow.