The Jewish Military Organization was an outgrowth of the Betar

Betar

The Betar Movement is a Revisionist Zionist youth movement founded in 1923 in Riga, Latvia, by Vladimir Jabotinsky. It has been traditionally linked to the original Herut and then Likud political parties of Israel, and was closely affiliated with the pre-Israel Revisionist Zionist splinter group...

 movement in Nazi-occupied eastern Europe. After Menahem Begin fled to Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 territory, Jewish veterans of the Polish Army and the National Military Organisation

Irgun

The Irgun , or Irgun Zevai Leumi to give it its full title , was a Zionist paramilitary group that operated in Mandate Palestine between 1931 and 1948. It was an offshoot of the earlier and larger Jewish paramilitary organization haHaganah...

 networked with Polish military officers

Officer (armed forces)

An officer is a member of an armed force or uniformed service who holds a position of authority. Commissioned officers derive authority directly from a sovereign power and, as such, hold a commission charging them with the duties and responsibilities of a specific office or position...

 to prepare for the insurgency against the Third German Reich. The military background of the organization was a useful attribute in an environment of tyranny and genocide. The Jewish Military Union, a branch of the Jewish Military Organization, was effective at fighting Axis forces in Warsaw

Warsaw

Warsaw is the capital and largest city of Poland. It is located on the Vistula River, roughly from the Baltic Sea and from the Carpathian Mountains. Its population in 2010 was estimated at 1,716,855 residents with a greater metropolitan area of 2,631,902 residents, making Warsaw the 10th most...

, Poland

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

.