The Force registered their third successive victory of the season when they beat the Chiefs 18-15 in Perth on Saturday night.
The home side were deserved winners and the groundwork to their stunning victory was a superb defensive effort which prevented the Chiefs from scoring any tries.
The Force dominated the early exchanges and opened the scoring in the 13th minute when captain Matt Hodgson dotted down after the Force went on the drive from a line-out close to the Chiefs' try-line.
The Chiefs struck back with a penalty from Aaron Cruden in the 18th minute but Sias Ebersohn restored the Force's five-point lead when he added a three-pointer shortly afterwards.
The rest of the half saw the Chiefs stepping up a gear but they could not breach the home side's defence and their only reward was two further penalties from Cruden.
The visitors were also dealt a blow in the 35th minute when Jamie Mackintosh was yellow carded after he stopped a Force maul illegally. Despite that setback, the Chiefs were up 9-8 at the break and they extended their lead, shortly after the restart when Gareth Anscombe succeeded with a penalty.
But with 14 men on the field, things went from bad to worse for the Chiefs two minutes later, when Hodgson scored his second try, after spotting a gap at a ruck close to the Chiefs' try-line.
Ebersohn slotted the conversion and with the score at 15-12 the hosts increased the intensity in their quest for victory. They thought they had extended their lead, shortly afterwards, when Nick Cummins pounced on a loose ball just outside the Chiefs' 22 before crossing over in the corner but the try was disallowed after television replays showed that he put a foot into touch in the build-up.
That didn't discourage them, however, and Ebersohn put his side further in front when he landed his second penalty in the 57th minute before Cruden replied with another three-pointer five minutes later.
That set up an exciting finish but although the defending champions spent most of the closing stages camped inside the Force's half, they failed to capitalise on their territorial advantage.
Each of their attacks was met by superb defensive work from the hosts who clung on to their lead until the end of the match.