He built a bridge of boats and rode back and forth across it on horseback for two days (a new spectacle, described in chapter 19). (Suetonius, Lives of the Caesars Caligula 19)
On the Mevanian road, on the way to see the river Clitumnus and its grove, he suddenly summoned the legions, conscripted them harshly, and marched north. (Suetonius, Lives of the Caesars Caligula 43)
He staged a mock war: he hid some German bodyguards across the Rhine and had them report, after dinner, that the enemy had appeared. (Suetonius, Lives of the Caesars Caligula 45)