During the Second World War, what was the Zagra-lin?

The "Zagra-lin" was a covert operation and part of the Polish resistance efforts during the Second World War. It referred to the "Zagranica linia" or "Foreign Line", a secret communications and courier network operated by the Polish underground state. This network linked occupied Poland with the Polish government in exile and the Allies, mainly in London.

Through the Zagra-lin, couriers carried vital documents, intelligence and military reports out of Poland, often risking their lives to evade German forces. It was an essential part of the Polish Resistance's efforts to maintain communication with outside forces during the war.

https://en.wikipedia.org/wiki/Zagra-Lin