There were Hundreds of Thousands of Resistance Members
The Polish Resistance was not a small group. There were several different Resistance groups that sprung up following German occupation. Some of them had differences of opinion, some wanted to support a Communist government for Poland, while others supported the government-in-exile. The largest resistance group was the AK, or Home Army.
The AK was formed in 1942 and had 100,000 members at the onset. It was originally known as the Union of Armed Struggle or ZWZ (Zwiazek Walki Zbronjnej), which formed in 1939 following the German occupation of Poland. It was renamed the Home Army in February 1942. The membership-only grew as time went on. At the start of 1943, the membership had grown to over 200,000 members.
As the Home Army became the main Resistance group in Poland, several other groups merged into it. The Bataliony Chlopskie was the second-largest Resistance organization, and had 160,000 men in its ranks by the summer of 1944. That summer that the Bataliony Chlopskie merged with the Home Army. The next largest resistance group was the National Armed Forces or NSZ and they had about 70,000 members in 1943. Some members of the NSZ merged with the AK, but the majority stayed separate. The Communist Resistance group Armia Ludowa had about 30,000 members and never merged with the AK.
When the AK reached its largest membership in the summer of 1944 it had anywhere from 300,000 to 500,000 members. It incorporated most of the other Resistance groups and received help from allies around the world. The Polish Resistance is credited as being one of the largest, if not the largest, Resistance organization of World War II.