12/29/2011 04:45 pm ET

2011 Protests: Violent Clashes Worldwide (VIDEO)

If there's ever been a year when civilians and police clashed as often and in as many different places across the globe, it's hard to recall. From Moscow to Athens, Occupy Oakland to Tahrir Square, hardly a day seemed to go by in 2011 in which people did not take to the streets for good old-fashioned civil disobedience somewhere around the world.

It's tempting to view the various clashes and uprisings this past year as part of a unified trend -- a global movement of the underclasses or the economically oppressed. Of course, the catalysts were often quite different, as were the stakes: in some places, young people rioted to express their outrage at government austerity measures that seemed disproportionately targeted at the poor (Greece) or students (London). Elsewhere, they rejected the insufficiently democratic reign of a corrupt leader (Rome), or the brutal police state of a corrupt regime (Egypt), or the entirely undemocratic policies of a corrupt system (Wall Street).

But if the causes seemed disparate, the components -- economic or political grievances, a lack of recourse through normal channels, the often harsh response of a police state -- were not so far off. Indeed, participants themselves often drew their own parallels, seeking common cause from their fellow protesters. In London, students tried to turn Trafalgar Square into Tahrir Square. In the actual Tahrir Square, demonstrators carried signs offering solidarity with protesters raided by police in Oakland.

One day this fall, shortly after Egyptian riot police had killed a demonstrator at a sit-in near the parliament, a protester was asked whether it was really fair to compare security tactics in Egypt to those in, say, New York. He replied simply, "Police are police." The same probably could be said for unfairness, and corruption, and violent suppression, or any of the other forces of unrest that boiled over in 2011.

Although it may not suit different movements to point out their common strands, it doesn't exactly demean them, either.

Above, watch some of the most brutal clashes between protesters and police in 2011.