The American tech giant has fought off stiff competition from Amazon to seal the money-spinning deal, which will run for a decade and is intended to help make the US defence department more tech savvy.
In response to the announcement, Amazon - which was actually thought to have been the favorite to land the sought-after contract with the US government - admitted to being "surprised" by the decision.
What's more, the company said in a statement that a "detailed assessment purely on the comparative offerings" would "clearly lead to a different conclusion".
Amazon is now reported to be evaluating its options, with the firm having ten days to decided whether or not to launch a challenge.
Meanwhile, in September, Amazon announced record quarterly profits of $2.53 billion in the three months to the end of June.
The technology giant - which was founded by the American billionaire Jeff Bezos - explained the eye-watering figures, which represented a marked increase during the same period last year, were helped by a rise in online sales and demand for its cloud-based services.
Reflecting on the impressive numbers, chief financial officer Brian Olsavsky explained: "It was a strong quarter. What I attribute it to is continued strength in some of our most profitable areas."