18 April 1989,
A group of conscientious objectors interrupted the passage of a military convoy in Vitoria. When the Spanish military went by, they chained themselves in the middle of the road and some stopped the tanks, so four of them managed to climb a tank. They sank, pushed and beat from there, and they also threw themselves into the chained.
Source:
Sabino Ormazabal, Grupo Bidea - 500 nonviolent actions, another way to tell the story (Fundación Manu Robles Arangiz).