[3] From 20 August 1914 he served in a military branch led by Władysław Belina-Prażmowski later becoming the 1st Uhlans Regiment of Polish Legions in World War I.

At the beginning of November 1918 he was sent to Chełm, where his loyalty resided with his squadrons who were forming the 1st Uhlans Regiment of Polish Legions once again.

On 26 January 1935, at the palace in Bialowieza, the Polish President Ignacy Mościcki gave him the rank of colonel with seniority and the 2nd most powerful position in the body of cavalry officers.

[11] Due to Colonel Heldut-Tarnasiewicz's initiative, all the families of the fallen in the battles for independence, they were awarded Polish lancers unit commemorative badges ID cards.

After the outbreak of World War II during the 1939 September Campaign, he was the commander of the Suwalski Reserve Centre and the Podlasie Cavalry Brigade (his successor in this function was General .

The Soviet invasion of Poland was the implementation of the Molotov–Ribbentrop Pact agreement signed in Moscow on 23 August 1939 by the Minister of Foreign Affairs of the Third Reich Joachim von Ribbentrop and the People's Commissar of Foreign Affairs of the USSR and the President of the Council of People's Commissars Vyacheslav Molotov.

[13] The Soviet aggressors attacked in the direction of Vilnius, Suwalki, Brest on the Bug, Lublin, Lvov and Kolomyia.

The most important battles of Polish troops (mainly by the Border Protection Corps, the Reserve Cavalry Brigade Wolkowysk [pl] (led by Heldut) and SGO Polesie) were: the defence of Vilnius, Grodno and Lvov and Fortified Zone Deer, as well as clashes in Szack, Wytyczno, Jabłoń and Milanów.

He held the position of commander of the Cadet School in the city of Edinburgh in Scotland, training men for the fight against the Axis powers.

Their relationship reaches back to World War I when Heldut joined the First Cadre Company founded by Józef Piłsudski.

The historic victory against the Soviets in the Polish-Soviet War stopped Bolshevism in spreading into Western and other parts of Europe.

The British military historian and general J. F. C. Fuller ranks the Battle of Warsaw (1920), and the Polish victory in the war, as one of the most decisive victories in history since it prevented Soviet influence from spreading to the borders of Germany, Hungary and Romania at a critical stage in these countries.

Throughout his military career, he continued to support the Allies of World War II in the struggle to help defeat Nazi Germany.

Even when he was forced to evacuate his homeland along with the Polish government-in-exile, he trained men for the front-line against the Axis Powers all the way from the highlands of Scotland where he was commissioned and stationed.

Starting in 1944, he was investigated by the Regional Office of Internal Affairs in Lublin part of the Provisional Government of the Republic of Poland, created by Stalin.