Tuhia he tomokanga mo tenei whitianga - I te hiahia ki te whai i nga tapuwae o tona papa, i whakaaetia a Johnson mai i a General Enoch Crowder ki te haere ki te Whare Wananga o California (i Berkeley) i reira ia i whiwhi ai i tana tohu Paetahi o nga Toi (me te honore) i te tau 1915 me tana Juris Doctor i te tau 1916 (te taarua i nga akoranga hei tohu i te haurua o te waa e hiahiatia ana). I whakawhiti atu ki te Judge Advocate General's Corps (JAG), mai i te Haratua ki te Oketopa 1916 i mahi ia i raro i a General John J. Pershing i Mexico me te Pancho Villa Expedition
I whakatairangahia ia ki te rangatira i te Hurae 1, 1916, i whakawhitihia ia ki te tari matua o te JAG i Washington, DC, i te Oketopa 1916. I whakatairangahia ia ki te rangatira nui i te Mei 15, 1917, a ki te rangatira rangatira i te Akuhata 5, 1917. I whakaingoatia ia hei Tumuaki Tuarua mo te Tumuaki i te Oketopa 1917, a i taua marama ano i whakaingoatia ia ki tetahi komiti o te Tari Pakanga mo te whakangungu hoia (kua uru te US ki te Pakanga Tuatahi o te Ao i te Paenga-whawha 6, 1917).