Last updated: 29.04.2026
Legal Framework – Polish Citizenship Act of 1920
Between 31 January 1920 and 18 January 1951, Polish citizenship status was governed by the Act on Citizenship of the Polish State of 20 January 1920 adopted shortly after Poland gained independence following World War I. Under this Act, Polish citizens could generally lose their nationality by acquiring foreign citizenship through naturalization in a foreign country.
However, men liable to compulsory military service could not automatically lose their citizenship. They required official approval – first from the Minister of Military Affairs, and later from the Minister of National Defense (after administrative reforms). This condition created the so-called “military paradox”: a man could be a foreign citizen under foreign law, but Polish authorities continued to consider him Polish until he was released from military liability or granted ministerial consent.
In practice, many emigrants who had chosen to obtain foreign citizenship in countries such as the United States or Canada were still legally considered Polish citizens under applicable law in Poland.
Who Was Liable to Military Service in Polish army and At What Age?
The age of liability to active military service changed several times, particularly in the period preceding and following World War II. The obligation to perform military service was closely linked with nationality law and affected individuals of Polish descent living abroad, including many Polish immigrants.
- 29 October 1918 – 17 November 1924 (Provisional Act on Universal Military Duty):
- Liability began on 1 January of the year a man turned 18,
- Ended with 31 December of the year man turned 50.
- 18 November 1924 – 31 August 1938 (Military Service Act of 1924):
- Liability began at 17 years of age,
- Ended with 31 December of the year man turned 50.
- 1 September 1938 – 27 May 1950 (amendments extending liability):
- Liability began at 17 years of age,
- Ended with 31 December of the year man turned 60.
- From 28 May 1950 onward (Act of 4 February 1950 on Universal Military Duty):
- Liability began at 18 years of age,
- Ended when a man turned 50.
Women were not subject to compulsory service. A Polish woman could join auxiliary units or medical corps in wartime, but the paradox concerned only men.
Loss of Polish citizenship
The critical question is: at what age could a man lose Polish citizenship automatically upon foreign naturalization, without needing ministerial consent?
Based on the statutes:
- Men born 1 January 1870 – 31 December 1887: lost Polish citizenship at the end of the calendar year they turned 50.
- Men born 1 January 1888 – 31 December 1889: lost citizenship at the end of the year they turned 60.
- Men born 1 January 1890 – 28 May 1900: lost citizenship on 28 May 1950, the day the new 1950 Military Service Act entered into force.
- Men born 29 May 1900 – 18 January 1901: lost citizenship on the day they turned 50.
- Men born after 19 January 1901: the link between military service and citizenship loss was abolished – the military paradox ceased to apply.
Thus, the paradox had a clear generational effect: men born between 1870 and 1900 remained under its influence, while younger generations were freed from this restriction by law.
Today these historical rules often affect individuals seeking to prove Polish citizenship or obtain confirmation of Polish citizenship, particularly descendants of emigrants of Polish origin.
Legitimate Children and the Military Paradox in Poland
Under the 1920 Citizenship Act, legitimate minor children under 18 followed their father’s citizenship. This meant that if a Polish father lost Polish nationality, his children born abroad could also be affected.
The law, however, introduced a safeguard:
- Legitimate children did not lose Polish citizenship if they had already reached adulthood before their father’s loss of nationality at age 50 or 60.
This protected adult children from involuntary loss of citizenship due to their father’s change of legal status.
These historical provisions remain highly relevant for descendants of Polish ancestors, including individuals whose Polish grandfather or other family members emigrated before or after World War II.
Many applicants seeking to acquire Polish citizenship or obtain a Polish passport today rely on documentation proving Polish roots, such as a marriage certificate, birth records, or archival documents confirming the citizenship of Polish parents.
An important nuance concerns men born before 31 January 1920 who naturalized abroad before reaching the age of military liability. In such cases, the “military paradox” did not apply. Since these individuals were not yet subject to compulsory military service under Polish law, they lost their Polish citizenship automatically upon foreign naturalization, without the need for ministerial consent. The paradox arose only in situations where naturalization occurred during the period of liability for active service.
Historical and Legal Significance
The military paradox was a legal anomaly between 1920 and 1951, reflecting the state’s priority of maintaining military obligations over personal nationality choices and the broader policy of the Polish government in matters of acquiring citizenship and military duty.
For thousands of emigrants, especially in the United States, Canada and Great Britain, this meant they were treated as Polish citizens long after they had naturalized abroad – a dual status that encapsulates the “military paradox.”
