Even before Washington returned, Dinwiddie had sent a company of 40 men under William Trent to that point, where in the early months of 1754 they began construction of a small stockaded fort. Governor Duquesne sent additional French forces under Claude-Pierre Pecaudy de Contrecœur to relieve Saint-Pierre during the same period, and Contrecœur led 500 men south from Fort Venango on April 5, 1754. When these forces arrived at the fort on April 16, Contrecœur generously allowed Trent's small company to withdraw. He purchased their construction tools to continue building what became Fort Duquesne.
what is the first group mentioned?