During his studies at the University of Lviv he was an active member of the Riflemen's Association. After the outbreak of World War I, he was conscripted into the Austro-Hungarian army and fought on the Italian front.

In November 1918, he reported for duty in the reborn Polish Army. He was appointed a commander of a battalion that took part in the Polish-Ukrainian War and then the Polish-Bolshevik War.

After the end of combat operations he decided to serve in the Polish Army. During courses and training he improved his qualifications as a staff officer, and worked in intelligence cells of the General Staff. In later years he commanded units of regiment and division strength.

In 1938 he took command of the Polish 10th Motorized Cavalry Brigade, the first fully motorized formation in the Polish Army. At its head he took part in the Second World War. Soldiers under his command successfully fought against German armored units in battles in Lesser Poland and Galicia. After the USSR invaded Poland, he decided to cross the border with Hungary. He quickly made his way to France, where he joined the re-created Polish Army and was promoted to the rank of brigadier-general. After Nazi Germany attacked France, he fought in Champagne, and after the surrender of France he evacuated through Africa to Great Britain.

He was given command of the 2nd Rifle Brigade, which he soon transformed into the 1st Armored Division. The unit was used in combat soon after the Normandy landings. The 1st Armored Division's combat trail began with the Battle of Falaise, where the Polish unit contributed significantly to the destruction of the encircled German forces. After the end of the battle, Polish units took up the pursuit of the retreating enemy, during which they liberated the cities of Belgium and Holland - Ghent, Passchendale and Ypres. The 1st Armored Division was able to save Breda from destruction thanks to the excellent offensive. The 1st ID ended its combat trail in Wilhelmshaven, where Stanislaw Maczek accepted the surrender of the fortress crew.

After the end of hostilities Stanisław Maczek remained in exile in Great Britain. In order to earn a living he did manual labour. In 1946 the communist Polish government deprived him of Polish citizenship. He was not forgotten by the Dutch who granted him honorary citizenship of this country and commemorated him in many places. Polish citizenship was officially restored to him in 1989.

He died at the age of 102 in Edinburgh. He was buried at the Polish soldiers' cemetery in Breda.