Conversation so far:
where was Frank Hague commissioner?
City Commission of Jersey City.
what years was he Commissioner?
1913.
how long was he commissioner?
1917.
what were some noteworthy things that happened while he was Commissioner?
Hague was named public safety commissioner, with control over the police and fire departments.
did the fire and police get along with him?
Hague immediately set about reshaping the corrupt Jersey City police force.
What did the police and fire department do when he did this?
Hague took steps to curb the police department's lackadaisical work ethic, punishing offenses that had gone unpunished for years.
who did he work closesly on his side?
an inner cadre of officers known as the Zeppelin Squad or "zepps" who were personally loyal to Hague alone.
was he ever betrayed by a Zepp?
The "zepps" would spy on, and report back to Hague about other members of the department.

Question: who did the Zepps spy on?
Self-contained rewrite: Who did the Zeppelin Squad officers spy on?