What is one basic weapon system used by infantry units?

The M16 rifle is a fundamental weapon system for infantry units, primarily due to its versatility, reliability, and the role it plays in individual soldier combat. As a standard-issue rifle for the United States military for decades, it is designed for close to medium-range engagements, making it an essential part of a soldier's equipment. Its semi-automatic and fully automatic firing modes allow for effective responses in various combat situations.

While the M249 machine gun and sniper rifle are also critical components of infantry operations, they serve specific roles—light machine guns provide suppressive fire and support, while sniper rifles are utilized for precision shooting at longer ranges. Tanks, on the other hand, are armored vehicles used for direct fire and personnel transport, making them a separate category of weapon systems not typically classified under standard infantry weaponry. Therefore, the M16 rifle stands out as a basic, essential weapon directly tied to individual infantry soldiers.