Complex sentence: The US Army Signal Intelligence Service (SIS) and OP-20-G were hobbled by bureaucracy and rivalry, competing with each other to provide their intelligence data, codenamed "MAGIC", to high officials.
Split into simpler sentences: The US Army Signal Intelligence Service (SIS) and OP-20-G were badly hobbled by bureaucracy. The groups had become rivals, competing with each other to provide their intelligence data, codenamed "MAGIC", to high officials.