Demonstrators tried to run in front of the convoys and others dumped garbage on roads Wednesday night to try to halt the transport of gear for an Army Stryker brigade that recently returned to nearby Fort Lewis from Iraq.
The demonstrations began peacefully, with more than 100 protesters chanting slogans, but rose in intensity as the night wore on.
Police kept their use of force to a minimum, said Cmdr. Tor Bjornstad.
"We've had officers spit on tonight," Bjornstad said. "They've had to put up with an awful lot."
Allie Van Nostran, 18, an Evergreen State College student, said people were shoved back to the sidewalk.
"I was shoved across my collarbone with a billy club," Van Nostran said.
Nearly 40 people were arrested in 10 days of protests in May 2006 when the equipment of the same Stryker brigade was loaded onto a ship in Olympia for transport to Iraq. All charges were later dropped because of problems with documents related to the case.