Sertorius (21.3-21.4)

Victory had now changed sides, and therefore Sertorius, contriving a safe retreat for his men and devising the quiet assembly of another force for himself, took refuge in a strong city among the mountains, and there began to repair the walls and strengthen the gates, although his purpose was anything rather than to stand a siege.

But he completely deceived his enemies; for they sat down to invest him and expected to take the place without difficulty, and thus suffered the Barbarians who were in flight to escape, and took no heed of the force that was being collected anew for Sertorius. And collected it was, after Sertorius had sent officers to the cities, with orders that as soon as they had a large body of troops, they should send a messenger to him.