Whakaotihia te rerenga e whai ake nei: I te tau 1862, ka uru a Sladen ki te Ope Taua o te Kotahitanga mo te Pakanga a-Iwi o Amerika, i whakauruhia hei tangata takitahi i te Kamupene A, 33rd Massachusetts Infantry Regiment. I uru ia ki etahi o nga whakaeke a te ope, tae atu ki te Pakanga o Chancellorsville me te Pakanga o Gettysburg. I whai wāhi a Sladen ki te Rā o Mei 13-15, 1864
Te Pakanga o Resaca. I a ia e mahi ana hei kaitohutohu i te tari matua o te ope taua, ka whakarere a Sladen i tana pou ki te whakauru i a ia ki te pakanga. Na tana tauira whaiaro i whakatenatena i ona hoa i te wa tino nui o te pakanga, a ka whakakotahi ratou ki te patu i o ratou hoa whawhai o te Rōpū. I te tau 1895, i whakawhiwhia ki a ia te Medal of Honor hei whakanui i tana toa o te Pakanga a-Rohe.