 During the Second World War, partisan resistance began earlier in San Marzano Oliveto than in other comuni in the region.On 24 and 25 December 1943, arriving first from Nizza Monferrato and later from Asti, soldiers of the Republic of Salò combed the area, searching every house for partisans.No partisans were found, but four hostages were taken and sent to Asti.