August 31 is a key date in the history of Donostia-San Sebastián. It marks the day on which, during the Peninsular War (1807-1814), victorious British and Portuguese troops that had been involved in laying siege to the (French-controlled) city that summer ran amok, razing Donostia-San Sebastián to the ground.
Donostia stood as the last major outpost of French control and the prize target for the combined allied powers of Britain, Spain, and Portugal in their attempts to crush Napoleonic French influence in the Iberian Peninsula. It was, however, well fortified and the siege of the city by the advancing troops under British command had lasted all summer.
When, finally, the allied troops did break through the main lines of defence on August 31, they ran amok, looting and pillaging from the innocent inhabitants of the city, which had been occupied by French forces for the previous five years. Most of the city was razed to the ground as a result, kept burning for several days thereafter, and had to be built again, practically from scratch.
The awful events of are remembered annually in Donostia with a nighttime torchlight procession taking place along August 31 street on this date.