Same role that the brown shirts had in the 1920's through 1930's. They plan to be the muscle that suppresses opposition to fascism. They are even calling liberals and progressives, "communists" who were the main targets of brown shirts in the 1920's. I think they are using Portland and other liberal cities to practice street fighting tactics in preparation for escalating the violence next year and especially during the 2020 election year.
Other actions that are reminiscent of the rise of Nazis to power in Post WW1 Germany are: Control of the police and courts. GOP is stacking the judiciary with their people. Nazis have infiltrated police departments and police have acted with the fascists in both Portland and Berkeley. ICE is his personal police force and the largest police organization in the country. Control of both the police and the courts are always key elements in dictatorship takeovers.
It is all an echo of the past, not an exact repeat. Trump's not ready for a take-over yet so there is still a chance we can get him out of office before he can seal the deal by replacing military leaders with his own people. Trump is also off golfing 100 days a year, which isn't exactly an indication that he even wants to rule the world. That and, Trump is wholly uninformed about the workings of the world. Still, I do see parallels between then and now.