During the Polish–Soviet War, he gained great fame for achieving a decisive victory in the Battle of Komarów, the largest cavalry engagement of the 20th century.

[1] Although the Rummel family felt Polish and spoke Polish at home,[2] they were in fact heirs to one of the oldest German families in Central Europe, tracing its roots to a certain Matthias Heinrich Freiherr von Rummel, a Livonian Brother of the Sword who in 1332 owned the Getzingen castle near Jülich in Westphalia and settled in Courland to support the Teutonic Knights in their struggle against the pagan Balts.

From January to early February 1918 on the order of General commander Eugene de Henning Michaelis, Rómmel was in charge of all Polish troops stationing in Kiev.

During this period he formed a separate Artillery III Corps consisting of three batteries, which he later commanded in Central Europe.

During the Russian Civil War, he commanded the Polish Light Brigade, a part of General Żeligowski's 4th Rifle Division.

During the Polish-Soviet War between 1919 and 1920, he took part in the fighting in the Vilnius region and also was a participant in the Latvian offensive (during which his unit captured Daugavpils).

In September 1920 he also fought with distinction in the ranks of Haller's Operational Group of Sikorski's 3rd Army during the Battle of the Niemen River.

[5][6] Under still uncertain circumstances, Rómmel and his staff were separated from his army and headed for Warsaw, arriving on the night of 7–8 September.

[6] Rydz-Śmigły gave him a signed order to "..defend the city as long as ammunition and food lasts, to hold as many of the enemy forces as possible.

Rómmel allowed Michał Tokarzewski-Karaszewicz to engage in further battles and operations to maintain the independence and the integrity of the borders, which became the nucleus for the Polish underground organization.

He was a good type of soldier, fit for the further development of innate abilities and ideal for protecting his own military units."

46 years later, former chief of staff Aleksander Pragłowski wrote that "Although skilled and talented, Rómmel was full of surprises.

It was shocking that he didn't make an effort to aid the Poznań Army or at least keep Warsaw free from Nazi slaughter for another month."

Rómmel left 9 volumes of Memoirs dating from as early as 1881 to 1939, which are currently located in the Department of National Archives in Wrocław.

Rómmel was married three times: from 1905 until 1932 to Maria Zofia Gobert, then to Irena Elwira Dębska until 1947, and finally to Janina Puchała-Puchalska (1911-1973).