Complex sentence: In June 2009 while taking part in anti-piracy operations off the Horn of Africa, "Portland" intercepted ten alleged pirates but because the suspects were not caught in the immediate act of piracy, the vessel was unable legally to detain them.
Split into simpler sentences: In June 2009 while taking part in anti-piracy operations off the Horn of Africa, "Portland" intercepted ten pirates. However, as they were not caught in the immediate act of piracy the vessel was unable legally to detain them.