Arsenal won their biggest victory of the season against the best team they've played in the toughest venue they've traveled to.
With their backs to the wall in their Champions League group, and as Napoli beat Marseille, Arsenal defeated Borussia Dortmund 1-0 thanks to a goal from Aaron "The New Zidane" Ramsey—his 11th of the season.
The Gunners remain at the top of Group F, ahead of Napoli on goal difference and goals scored. Arsenal have to play Napoli and Marseille once more each before the group stage is done.
Let's look at six things we learned from their vanquishing of Dortmund.
Of course it was Aaron Ramsey.
Of course when Olivier Giroud nodded down Mesut Ozil's cross, Ramsey was the man there to bravely stick his head out and poke the ball past Roman Weidenfeller.
Who else was it going to be?
Ramsey cannot stop doing things right. His positioning was perfect because his work rate was tireless as ever. His willingness to put his head near Neven Subotic's outstretched boot is indicative of the fearlessness that entered his game toward the end of last season, and which has made him one of the world's best midfielders.
Remember when Arsenal lost to Dortmund two weeks ago and Chelsea a week after that? Remember how pundits openly questioned whether the Gunners could measure up against elite opposition?
If their defeat of Liverpool didn't do it for you, surely this did. Dortmund are arguably a better team than last year, when they came so close to defeating Bayern Munich and winning the Champions League.
Arsenal did not swagger into Signal Iduna Park and manhandle the home side; in fact, they are somewhat lucky to be leaving with three points. But their ability to stand up to—and overcome—one of the most difficult tests that can possibly be given them says volumes about this Arsenal team.
It is impossible for any Arsenal fan to imagine a side that Arsene Wenger would have fielded two or three years ago standing up to one of the most potent attacking machines in the world and keeping a clean sheet.
Arsenal were remarkably composed in defense, led by the immense Per Mertesacker, who turned in perhaps his best performance of the season and continues to force Wenger to include him in every starting lineup.
He and Laurent Koscielny remained disciplined at the back and dealt with inevitable chaos as best they could. They occasionally had to rely on Wojciech Szczesny, but less experienced and composed defenders would have blown the game for Arsenal.
Perhaps because of Aaron Ramsey's spectacular form and/or Arsenal's surprising success, the best period of Wojciech Szczesny's career has gone largely unmentioned.
This is a good thing, as the Pole can quietly improve himself and develop without the media scrutiny that has so often surrounded him during his maturation process. But after his masterclass versus Dortmund, Szczesny might get thrust into the spotlight once more.
As usual, he firmly commanded his penalty box and gave his defenders the confidence they needed to be aggressive.
When called into action, he was faultless. After wonderfully saving Marco Reus' header, he delivered a truly world-class save to dive and get a strong hand to Jakub Blaszczykowski's effort.
There is an old cliche that title-winning teams find ways to win games against inferior opponents when they are not at their best.
It doesn't quite apply here because Arsenal were at something approaching their best and Dortmund are superior opposition. But a modification of the cliche still applies, for Arsenal still found a way to eke out three points.
That is the mark of a side that has something intangible going for it during a special season. The Gunners have not been able to find a way to squeeze out tight results against upper-echelon opposition with any regularity in the past. Perhaps they are breaking that trend.
All plaudits aside, if Arsenal want to seriously contend for their first-ever Champions League trophy, they will have to be able to beat sides like Borussia Dortmund by using a bit less luck.
Snatching three points against the run of play by playing pugnaciously says something about a team, but so does the fact that they had to do so in the first place.
Andrew Mangan wrote correctly for ESPN FC that "Dortmund are a far better team." It's true: Jurgen Klopp's side is tactically very similar to Arsenal but executes the same philosophy with more pace and a much more clinical edge.
In players like Mesut Ozil, Aaron Ramsey, Santi Cazorla, Olivier Giroud, Arsenal have the ability to raise their game to Dortmund's level. Regardless of whether the Germans are eliminated from this year's group of death, Arsenal need to look to Dortmund as an example if they wish to win the Champions League.