The ummbaran troops where forcing their troops onto the republic forces. Up in his tower pong krell was plotting the destruction of the siege of umbara when he realised he could just get the 501st and the 212th to kill each other so that's what he did. "Waxer tell your commder to head to these coordinates x 277 y 433 z 543 the ummbaran leader will be their." Then he told Rex the same coordinates now alled he had to do is wait. After two hours the clones came back to Krells tower where he realised that if you want to do something right do it yourself.