Kammala jumla mai zuwa: Daga 1903, Mischchenko ya zama kwamandan Brigade na Trans-Baikal Cossack. A lokacin Yaƙin Russo-Japan na 1904-1905 ya umurci wani Brigade na Cossack na Gabas-Baikal, wanda ya kasance mai aiki a yawancin yaƙe-yaƙe na wannan yaƙin. Da farko, sojojinsa sun kasance a Koriya, tare da umarni don hana saukowar Sojojin Farko na Japan da tafiya zuwa Manchuria. Duk da haka, bayan wasu ƙananan rikice-rikice, Mischchenko ya janye a fadin kogin Yalu. Ya taka muhimmiyar rawa a bangarorin Yakin Kogin Yalu, kuma ya kasance wani ɓangare na tsaron Rasha a yakin Hsimucheng, da yakin Te-li-Ssu. A yakin Liaoyang da kuma a
Yaƙin Shaho, ya umurci rukunin sojan doki na Rasha da ke rufe masu tsaron baya na Rasha. An ba shi mukamin Laftanar Janar a watan Oktoba na 1904, kuma an nada shi kwamandan sabon Cavalier Corps a watan Disamba na 1904 kuma ya jagoranci babban hari zuwa kudu a ranar 6 ga Janairu 1905 tare da mahayan dawakai 6000 a kan manufa don lalata kayan aikin Japan da aka adana a Niuchang. Wannan aikin ya kasance bala'i, kuma sojojin sun dawo bayan kwana goma sha biyu tare da asarar rayuka masu yawa. Ya ji rauni a kafa a lokacin yakin Sandepu kuma kodayake an sake shi a matsayin kwamandan Cavalier Corps a watan Maris na 1905, ba a cikin yakin Mukden ba.