The Twilight Army approached Riven. We were rather broken up and dysfunctional at this point, and I wasn't sure who was who. We were essentially lost. Once we were attacked by the defenders of Riven, we realized we were outnumbered due to the fact that we simply didn't have the organization level others had, so many of us were lost in the forest. We moved inside the city, but weren't sure who to attack. Suddenly, fighting broke out and it became quickly apparent that we could hold them off, but not forever. So birds were sent to Syrio and Brevias calling for their aid when the battle truly began.
The crater was there when we got there.
Edit: Note that I did not order anyone to attack Riven. We were struck first from the town, so we struck back. We did not intentionally go to Riven, we were just lost.
Says a lot for my leadership skills :P