OAKLAND, Calif. — In most cities, the Occupy movement has been thrown on the defensive, struggling to regroup and plan new protests after being evicted from its encampments by the police.

Not in Oakland.

Long the most militant Occupy branch, Occupy Oakland has continued to push the movement’s campaign against the wealthiest 1 percent even after losing its perch in front of City Hall. It spearheaded a one-day action on Monday in which thousands of protesters rallied at West Coast ports from San Diego to Anchorage, effectively closing the Ports of Portland and Longview, Wash., and largely shutting the Port of Oakland.

In the process, Occupy Oakland has cast itself as the true champion of America’s workers, creating a potentially troublesome rift with the Occupy movement’s sometime allies in organized labor.

Several labor leaders criticized the plan to disrupt the ports, which cost many longshoremen and truck drivers a day’s pay. And union officials were irked by Occupy Oakland’s claim that it was advancing the cause of port workers even though several unions opposed the protests.