The American victory at Cerro Gordo in April 1847 was followed by what was anticipated to be a major effort against the town of Puebla. However, local officials decided to open their gates to the advancing army in the hope of preserving their town. Slight resistance was put up by Santa Anna's retreating army, but American forces occupied Puebla in mid-May. The heaviest toll in this engagement was taken by the town's tainted water supply, which incapacitated hundreds of Winfield Scott's soldiers. The able-bodied then advanced toward Contreras.