JCB has landed a £115m ($142m) order to produce 1,600 rough terrain vehicles for the army to use around the world on tasks including loading and unloading aircraft and shipping containers.
The 400 workers at the firm's plant in Wrexham will be involved in producing axles for the trucks.
JCB said it was one of the biggest single orders in its 71-year history.
Chief executive Graeme Macdonald said: "This order is fantastic news for JCB and a great way to start the New Year.
"I congratulate everyone who has worked to secure this valuable contract."
A Wrexham factory is to play a key role in supplying the US Army with a huge fleet of forklift trucks.