 Nyorai kupfuurira kweiyi ndima - Pakutanga kweHondo Yenyika, Zimmerman akasiya Academy ndokuedza kubatana neUnion Navy, asi akarambwa nokuti akanga achiri muduku zvikuru. Pashure pokuchinja zvimwe zvinhu, akagamuchirwa, akava mukuru mukuru uye akapiwa basa muMississippi River Squadron. Paaiva muNavy, ngarava yake yakarohwa netorpedo iyo yakauraya vafambisi vengarava vakati wandei ndokumukanda muRwizi rweYazoo. Akatora chikamu muHondo yeSaint Charles uye Duvalls Bluffs uye akashanda nekusiyanisa panguva yekutorwa kweArkansas Post muna 1863, mushure mezvo akasimudzirwa kuEnsign. Munguva yeVicksburg mushandirapamwe muguta rake, Zimmerman akaiswa mutariri wechikepe chemarata uye akatumirwa kuRwizi Yazoo, achiita kubudirira kurwisa Confederate blockade paVicksburg muna Kubvumbi 1863. Munguva yemushandirapamwe, akabatanidzwa mumamishinari akati wandei uye akasimudzirwa kuita Master uye Officer we padivi vhiri steamer USS Ouachita mushure mekuzvipira kweVicksburg kwaakabata kusvika pakupera kweHondo. Mukati mokukombwa, imba yake yekare nebhizimisi rababa vake zvakaparadzwa. 