"Vietnam: 1965-1975" re-creates the longest, most complex, and least understood conflict in US history in all of its military and political aspects. The rules include detailed treatment of movement, terrain, search and destroy operations, special operations, firepower, airmobility, riverines, brigade-level formations, limited intelligence, and auxiliary units in each scenario."
That's the blurb from the back of the original Victory Games edition of the game.

There are several small scenarios and a couple of campaign games. Each year is divided into four seasons (Spring, Summer, Fall, and Winter), and each season has two turns (so, roughly 6 weeks per turn). The map scale is roughly 6 miles per hex and units are, generally, battalions or regiments. During the operational phase, players take turns (who gets to operate is determined by the NLF player) conducting operations with their units to destroy the enemy, clear the roads, take towns and cities, or just reposition units. In the Campaign Game, during Seasonal Interphases, each player decides whether and how many additional units and/or resources to bring in to the fight. The game features hidden VC units, airmobility, riverines, national morale, pacification, ARVN effectiveness, and many other nuances that allow the player to grasp the some of the experience of what it might have been like to conduct the war in Vietnam.

An updated reimplementation of the Victory Games' classic.
This edition changes some of the rules as well as clarifications. Components are also upgraded from the original printing.
See developers' word.

COMPONENTS

3 22"x34" maps (approx. 66"x40")
Rulebook
Playbook
2 11"x17" Seasonal Interphase (Population Control Reference, Strategic Bombing, Blockade and Morale Chart/Sheet)
2 11"x17" Operations Player Aid Card (General Operations, Search & Destroy, Security and Bombardement flowcharts)
2 CRT/TEC player aid cards
1 Sequence of Play card
US, SVN, and NLF Record Sheets (3)
Population Control Record Sheet
Allied and NLF Holding Boxes (2)
4 sheets 9/16" counters
2 sheets 1/2" counters

(description from publisher's website and BGG user's comment)