Giovanni van Bronckhorst revealed Rangers fine-tuned no fewer than three Europa League masterplans before they dumped out Dortmund.
The Ibrox boss savoured a huge aggregate victory over the Bundesliga giants that books a place in the competition's last 16 for a third consecutive season.
Captain James Tavernier struck twice to secure a thrilling 2-2 draw on the night and usher Rangers through with a 6-4 advantage over the two legs.
With Dortmund resurgent in the first-half, Van Bronckhorst introduced some tactical tweaks that reinvigorated his team after the interval, withdrawing Borna Barisic for Leon Balogun and switching to a back five.
And the Rangers manager told BT Sport: "It was purely tactical. Before the game, we trained three different plans for today and this was Plan C! We needed it.
"I knew, with the score in mind, we had to have the scenarios in place to be executed and the guys did really good.
"It's very important for everyone, it's a big moment for us as a club.
"We could make a lot of people proud tonight with our performance, and we did. It was a difficult game again.
"We had a really good start but after we conceded two goals, at half-time I had to change the system, the system we talked a lot about it in meetings.
"I think the system worked really well for us in the second-half."
