Rubuta ci gaba don wannan sakin layi - Eglin ya shiga Indiana National Guard a 1911 yayin da yake dalibi a Kwalejin Wabash, kuma ya fara aikin tarayya a watan Yunin 1916, yana aiki a kan iyakar Amurka da Mexico
Ka yi haƙuri. A cikin 1917 an ba shi izini a cikin Indiana Guard bayan Amurka ta shiga Yaƙin Duniya na I kuma an sanya shi horo na matukin jirgi. Bayan samun cancantarsa a matsayin matukin jirgi da kwamiti a cikin Sashen Jirgin Sama, Rundunar Sojan Amurka, Eglin ya kasance a makarantar a matsayin mai koyar da jirgin sama. Eglin ya sami kwamiti na yau da kullun a cikin Sabis na Jirgin Sama a ranar 1 ga Yuli, 1920 kuma ya umurci rundunonin jiragen sama da yawa a Amurka da Philippines.