 From there the progress slowed even further as the army made its way to the Monongahela River.Washington fell ill with dysentery en route, and only rejoined the column on July 8, when it was nearing the Monongahela.The next day, after Lieutenant Colonel Thomas Gage's light infantry had crossed the Monongahela about from Fort Duquesne, they stumbled into a French and Indian force that had been sent to locate them.