2nd Infantry in Viet Nam?

Hey lisajohn-4. I'm sorry to be late to the show, but I just checked this movie's pages for the first time after seeing it last night on AMC.

I have your answer.
Short version: until 1965, 1st Cavalry Division had been stationed in South Korea, and 2nd Infantry Division was at Ft. Benning. In '65, the divisions' names (their "colors," to use Army terminology) and the names of their subordinate units were essentially just swapped from Korea to Ft. Benning and vice versa. Troops stayed in place, only the unit names were changed.
Except that: "1st Cav" didn't stay quite the same back at Ft. Benning. It's unit names went to fulfill and replace the experimental 11th Airborne Division, and "11th Abn" was disbanded/retired.

In other words, the Army went into 1965 with 3 nominal divisions (of those I mentioned), and ended the year with 2:
-- the unit names of 2nd Div from Ft. Benning replaced the unit names of the 1st Cav for troops already in Korea
-- the unit names of 1st Cav went back to Ft. Benning, and were applied to the troops formerly assigned to the 2nd Div, and "fused with" the mission and identity of "11th Airborne" to create a new type of division-- "Air Cavalry."

If I'm making that too complicated, here it is from wikipedia:
http://en.wikipedia.org/wiki/1st_Cavalry_Division_(United_States)#Vietnam_.E2.80.93_1st_Cavalry_Division_.28Airmobile.29
In 1965, colors and subordinate unit designations of the 1st Cavalry Division were transferred from Korea to Fort Benning, Georgia, where they were used to reflag the existing 11th Air Assault Division (Test) into 1st Cavalry Division (Airmobile). Concurrently, the colors and subordinate unit designations were transferred to Korea to reflag what had been the 1st Cavalry Division into the 2nd Infantry Division.

Remember in the movie, when the troops are still at Ft. Benning, and Moore and all the infantry guys we see are wearing the 2nd Div. patch-- you might have noticed that "Snake" and "Too Tall" and all the helicopter crew are wearing a now-forgotten little blue-and-white shield with tiny wings on it and a little red "11" inside it. That was the patch of the 11th Airborne Division. That inclusion in the film is a very subdued --but surprisingly accurate-- nod to the "merging" of the 11th Abn. with the infantry troops of the 2nd Inf Div already at Ft. Benning (who were "reflagged in place" as "1st Cav" simultaneously as "11th Abn" was retired and replaced by "1st [Air] Cavalry").
So as for your notion, lisajohn-4, that 2nd Inf Div was in Korea for most of the Vietnam-War era: correct, and "it went there" concurrent with the guys in the movie putting on the 1st Cav patch.
The point you cited in your last post, about 2nd Div at Ft. Benning being trained-up as a STRAC unit probably explains the Army's decision to keep them in place and use them as the troops of the new "Air Cav" division.

Now, if I can wax a little historically reflective: that "reflagging" of units called "airborne" and incorporating the use of helicopters was re-done about 15 years later. My wiki citation above indicates that the Army was already trying to re-organize an "Airborne" division as a helicopter "Air Assault" division, in 1965. And the U.S. Army's modern "101st Airborne Division" is essentially what the "1st Cav" was in Vietnam: a helicopter-mobile "air assault" Infantry division. The name "Airborne" for the modern 101st is only a historical honorific, just like calling 1st Cav "cavalry" was in Vietnam; just as logical or illogical as a name for helicopter Infantry, depending on your viewpoint. By the same logic, the Army could decide to re-organize the "1st Armored Division" as helicopter Infantry and yet keep calling it "Armored."

And lisajohn-4, I am guessing from your original post, that your dad was in the 38th Infantry Regiment of the 2nd Div in WW2 (that's how the nomenclature works). As late as my duty with the 2nd Div in Korea in the mid 1980s, there was still a remnant of the 38th Infantry in the Division-- 1st Bn., 38th (a.k.a. "1/38 Inf"). But back to weird "reflagging:" in September 1986, that battalion was redesignated as either 1st or 2nd Bn of the 503rd Infantry, a traditionally Airborne Infantry unit; their regimental crest depicts parachutes! (It was reflagged along with a neighboring infantry battalion, 1st Bn., 23rd Inf. --another old 2nd Div legacy unit-- as 1st and 2nd of the (new) 503rd, but I don't remember which became "1st" and which became "2nd.")