Arsenal manager Arsene Wenger felt his side's defensive discipline was the key to their crucial 1-0 win over Borussia Dortmund in Champions League Group F.
Wenger described his players as "naive" when they lost to a late goal at home to Dortmund last month but said they executed his plan perfectly in Germany.
"We had a united, focused performance, especially defensively," Wenger said.
"It was a question of being focused and intelligent, and to wait for the moment to create openings in their defence."
The Gunners did precisely that, with Aaron Ramsey scoring what proved to be the winner with his side's first effort at goal in the 62nd minute.
Dortmund, last season's beaten finalists, had failed to score in only one of their previous 60 home games at their Westfalenstadion home, where they had won their previous eight Champions League ties.
"We had a difficult period at start of second half, but after we scored I felt we could have scored a second goal and we were less under pressure," Wenger added.
"Overall it's a huge win here. If you look at the results they have made at home in the Champions League, not many teams have achieved that."
Dortmund's best spell came at the start of the second half but, after Ramsey scored, they rarely threatened.
"We looked more stable defensively because we have experience in midfield not to lose the ball in stupid positions," explained Wenger.
"Dortmund are especially dangerous when you lose the ball, and to counter that, you need maturity. If you have a very young team tonight you would be overrun and lose that game by a very high score. We look more stable defensively."
Arsenal are top of Group F but their progress to the knockout stage is far from certain. Marseille are out of contention but either the Gunners, Napoli or Dortmund will have to settle for a place in the Europa League.
"I have a lot of respect for Dortmund because they are a very good side," Wenger said.
"Unfortunately this group is a very strong group, and one of the big teams will have to pay a heavy price. I hope it will not be us."