Complex sentence: In the meantime both "Pomone" and "Tenedos" were closing on "President" and by 9.05pm, "Pomone" had caught up, firing two broadsides at "President", after which Decatur once again indicated his surrender.
Split into simpler sentences: In the meantime both "Pomone" and "Tenedos" were closing on "President". By 9.05pm, "Pomone" had caught up, firing two broadsides at "President", after which Decatur once again indicated his surrender.