Complex sentence: J. E. Quigley, Archbishop of Chicago, realizing the Croatian Catholic community's need for spiritual guidance and sustenance, requested the Holy See to send a Croatian priest to work among his people in Chicago.
Split into simpler sentences: J. E. Quigley, Archbishop of Chicago, realized the dire need of Croatians for spiritual guidance and sustenance. He requested the Holy See to send a Croatian priest to work among his people in Chicago.