The Poles had been bloodily defeated in the rebellions of the 19th century, and the status of a Russian officer was not free from conflict. Being a Finn, Mannerheim’s position may have been easier than that of his colleagues, and he was able to state that one of his relatives had been living in Poland. He got to know the Polish societies, e.g. the Zamoyskis, Potockis, Krasinskis and Radziwills. Counts Maurice and Adam Zamoyksi and Prince Zdzislaw Lubomirski with his wife Marie Lubomirska were some of his best friends. Mannerheim’s friendship with Princess Lubomirska was deep and continued in correspondence and in personal encounters for a long time.

At the beginning of 1914, Mannerheim was afforded the command of the Cavalry Brigade in Warsaw, a post which had been vacated. He left the Warsaw hunting club in late July to mobilize his brigade, and in a few days’ time Germany declared war against Russia. Mannerheim’s troops fought in southern Poland, and he stood witness to the destruction of the Polish countryside. Warsaw was occupied by Germany.

After the end of the First World War, Mannerheim visited Poland and met his Polish friends.