The New York Police Department puts an endless list of tasks on the shoulders of its so-called white shirts — the commanders atop an army of lesser-ranking officers in dark blue.

But the portfolio of the white shirt has now unexpectedly grown to include the role of enforcer.

As the Occupy Wall Street protests, which began on Sept. 17, lurch into their third week, it is often the white shirts who lay hands on protesters or initiate arrests. Video recordings of clashes have shown white shirts — lieutenants, captains or inspectors — leading underlings into the fray.

White shirts led the face-off with protesters on the Brooklyn Bridge on Saturday afternoon. The episode provided no viral YouTube moments, as the senior officers avoided confrontations with the demonstrators. Yet as hundreds of arrests were made, chants of “white shirts, white shirts” could be heard.

And a white shirt is the antagonist in the demonstrations’ defining image: Deputy Inspector Anthony Bologna’s dousing of some penned-in women with pepper spray on Sept. 24, which seemed to surprise at least one of the blue shirts standing near him on East 12th Street, near University Place. The department is investigating the spraying.