A few members of the 309th Legion stupidly made the decision that an explosive might help thin the Sith and the CIS troops. The group snuck behind the CIS forces and placed a couple Detpacks behind them. After they returned to the Republic's side of the Temple, they detonated the charges. The explosion not only caused only a few amount of CIS casualties, but it caused part of the Temple to cave in, including the entrance to the temple, cutting off the chance of reinforcements.