The Vanguard class phaser tank is a type of military vehicle used by the Federation.
These tanks were an essential requirement among Federation colonies and were both the first and last line of defense. While their Phaser array is no substitute for a starship grade version of the weapon, its presence does help reassure the colonists that they are protected from harm. A sophisticated anti-gravity system allows the Vanguard to float across its environment in a fast and speedy fashion.
The crafts shield system makes it a resilient foe to face despite it not being the strongest of deflectors. This combined with the phaser array allows these tanks to deter invaders from entering Federation colonial sites. When an experienced Security officer is present on the tank, its capabilities are further enhanced with the dedicated training and experience of its pilot. (TOS video game: New Worlds)