Complex sentence: Doundoulakis established a communication point for the wireless radio in an abandoned Jewish textile factory whereby daily encrypted messages were sent to OSS Headquarters in Cairo, disclosing the location of German troops as well as maritime activities of Axis ships in the port of Salonica.
Split into simpler sentences: Doundoulakis established a communication point for the wireless radio in an abandoned Jewish textile factory. Daily messages were sent to OSS Headquarters in Cairo, which contained the locations of German troops, including maritime activities in the port of Salonica.