Kammala jumla mai zuwa: Iyalinsa sun yi hijira zuwa Amurka lokacin da yake yaro, tare da taimakon Hebrew Immigrant Aid Society. Ya tafi makaranta a Connecticut, ya kammala karatu a 1910. Maimakon yin karatun injiniya a Jami'ar Yale, matashin Horwitz da abokinsa sun yanke shawarar buɗe kantin sayar da kayan masarufi a Manhattan. A matsayin memba na National Guard na Amurka Horwitz aka kira a cikin sabis karkashin John J. Pershing su shiga a cikin
Tafiya ta Pancho Villa. Lokacin da ya dawo, ya gano cewa kasuwancin kayan masarufi ya rushe. Horwitz sa'an nan kuma ya yi aiki a yakin duniya na farko a Faransa a matsayin wani sergeant, kuma a matsayin wani sojan doki a Argonne.