At the time, the franc had been steadily gaining against the entire basket of G8 currencies. In fact, before the intervention, the Swiss franc had surged more than 13% against the euro in 2011. After the SNB intervened, the Swiss franc immediately weakened, snapping four days of gains against the euro and causing the EUR/CHF to shoot up like a rocket, clearing over 1,000 pips in just three hours.
As shown in this report: