So, Lewis Hamilton did exactly what he said he had gone to Belgium to do - he won the race. And in doing so, he kept Sebastian Vettel's Ferrari at bay for the entire 44 laps, leading it home by 2.3 seconds.
But it was not the emphatic victory that many had expected of Mercedes at this high-speed venue.
Previously this season, most notably in Canada and Silverstone, Mercedes had given Ferrari a good kicking. Here it was a very different story. Here, Ferrari had the advantage.
Was Hamilton's 58th win, in his 200th Grand Prix, due then to track position, or race pace?
"Qualifying was good for us," Hamilton said, as well he might, having equalled Michael Schumacher's 68 pole positions. "But if I hadn't had the lead I would not have been able to win, so it definitely wasn't on race pace."
Yet again he reiterated that the Ferrari had the edge on that all weekend, and if anything should sound all the alarm bells and put Mercedes on red alert, it is that.
For most of the year Mercedes and Ferrari have been pretty evenly matched, though the silver cars have had the advantage when the downforce has to come off, and the red ones when it has to go on - read Montreal and Britain; and Monaco and Hungary respectively.
They (Ferrari) brought a comprehensive update to Spa... to optimise ride height and rake angle... The changes seem to have worked extremely well, and though he got outfoxed by Hamilton, Vettel said he was very happy all weekend with his car's performance.
But now Ferrari appear to have the advantage even on tracks with low downforce, despite Mercedes bringing an engine update here.
Vettel said in Hungary that the team had identified the areas in which it believed the SF70H to be weak, and they brought a comprehensive update to Spa.
To optimise ride height and rake angle, both critical aerodynamic factors, they introduced a new front suspension, which was complemented by a revised floor and wings, front and rear.
The changes seem to have worked extremely well, and though he got outfoxed by Hamilton, Vettel said he was very happy all weekend with his car's performance.
Hamilton explained how that outfoxing started as a mistake on his engine mode settings as he prepared for the restart.
"Initially I got a very good start when we were on the back straight, I got a real good pull away," he said. "I was able to catch him out, as I did in Baku on the three or four starts with the safety car.
"I didn't have the right power mode and then he started catching me up.
"Initially it felt like a mistake, but in actual fact it was a really good thing, because if I came out of the last corner with that gap, he would have had the momentum, being three or four car lengths behind, to really propel and really get a good tow and slip past me. It worked out perfectly.
"I ran wide in Turn One with a small lock-up because my front tyres still weren't up to temperature, and I could hear him get on the gas sooner than I did. And then as we were going down that straight I didn't keep it fully lit the whole way, I was at 90 per cent throttle, just to keep him as close as possible.
"I knew he wasn't going to come by, because he knows I would overtake him then at the top part with the tow.
"As we were going up Eau Rouge, that's where I really gave it maximum power. We got to the top and he had no space to really propel himself, so he just pulled out alongside but couldn't pass. I was really happy with that."
Vettel was philosophical in defeat, and may have been the happier man as they left for Italy.
"The positive thing is that we had very good race pace," he said. "Overall the car was very good. We haven't changed too much since Silverstone, which was just a bad weekend, but we have improved the car too. If we were to go back to Silverstone now, we would be a lot better. It is a big step, so I'm very, very happy."
And, ominously for Mercedes's title hopes over the remaining eight races, he added: "I don't think we have a circuit which we should fear coming from now."
Victory in Belgium was crucial to Hamilton's title hopes, but another acid test will be Monza, which needs even less downforce than Spa, and is a real power track. If Ferrari are as close there, Mercedes should really be worried.