Whites boss Andy Hessenthaler hailed his depleted Dover squad after they reached the last 16 of the FA Trophy on Tuesday night.
Adam Birchall’s deflected strike just before half-time was enough to see Whites through after a 650-mile round trip to Blue Square North Fleetwood, who suffered their first home defeat of the season in the re-arranged second round tie.
Hessenthaler, who was forced to name himself in the starting line-up, said: "It’s one of our biggest results since I’ve been at the club.
"Nobody gave us a chance, we were the underdogs and we hadn’t been able to do much preparation.
"But we knew that if we could keep it tight early on, then we would have a chance and full credit to our players, they were phenomenal."
Dover will travel to holders Stevenage or Vauxhall Motors in the third round of the FA Trophy. The tie is due to take place on January 30.