Complex sentence: Initial combat experience with Excalibur in Iraq in the summer of 2007 was so successful, with 92% of rounds falling within of the target, that the US Army planned to increase production to 150 rounds per month from the previous 18 rounds per month.
Split into simpler sentences: Initial combat experience with Excalibur in Iraq in the summer of 2007 was highly successful, with 92% of rounds falling within of the target. It's performance was so impressive that the US Army planned to increase production to 150 rounds per month from the previous 18 rounds per month.