wˌɛn ðiːz wˈɜːks wɜːɹ ˌʌndɚ wˈeɪ, ˌɛndʒɪnˈɪɹ mˈeɪdʒɚɹ ˈælbɹɛxt hˈaɪnɹɪtʃ ʃɹˈoʊdɚ pɹəpˈoʊzd ɐ bɹˈæntʃt sˈɪstəm ʌv ˈæntaɪmˈaɪn tˈʌnəlz tə ðə hˈaɪ mˈɪlətˌɛɹi kˈaʊnsəl ɪn ˈɜːli wˈʌn θˈaʊzənd sˈɛvənhˈʌndɹɪd sˈɪksti fˈoːɹ.
When these works were under way, engineer Major Albrecht Heinrich Schroeder proposed a branched system of anti-mine tunnels to the High Military Council in early 1764.