After finishing second in the first European Championships at Turin in the 5000 m in 1934, Kusociński decided to retire from athletics, but made a comeback in 1939 by winning the 10 000 m at the Polish National Championships.
Despois de rematar segundo nos primeiros Campionatos de Atletismo de Europa en Turín nos 5.000 m, Kusociński decidiu retirarse do atletismo, aínda que volveu en 1939 gañando os 10.000 m nos Campionatos Nacionais de Polonia.