"the first contingent" is correct and usable in written English.
You can use it when referring to a group of people that are among the first to do something. For example: "The first contingent of students arrived at the school yesterday."
In 1848, the first contingent sailed to Liberia.
The first contingent of 150 African Union peacekeepers arrived in Darfur, with a mandate to protect AU observers.
But when the first contingent was freed last November, 150 turned out to be ordinary criminals rather than people who had been locked up for politically motivated actions.
Talk story about the new Secretariat Building, which was scheduled for occupancy for fall, but is now being moved into by the first contingent of….
Talk story about the new Secretariat Building, which was scheduled for occupancy for fall, but is now being moved into by the first contingent of U.N. employees.
The first contingent, from Honduras, Nicaragua and El Salvador, the areas hit hardest by the hurricanes, arrived almost a year ago.
Flying in from Manila's Vilamor air base, they were among the first contingents of the ballooning aid programme actually able to reach those in need.
And in many ways, matters went swimmingly — until, as the first contingents of athletes were transported across London to the Olympic Village, they went spectacularly wrong.
He intercepted the first contingents of army construction troops on the Bozeman Trail that summer, holding them prisoner for more than two weeks.
Although the first contingents from the north were prepared to leave in 1217, Frederick was not among them, partly because he underestimated his capacity to resolve his problems in Germany and Italy and partly because of the speed of preparations for the Crusade.
In May 1147, the first contingents of crusaders left from Dartmouth in England for the Holy Land.
