Is it required to say 'So Help Me God' during the Oath of Enlistment?

Nope! All about persona choice.

A good reenlistmemt officer will take a few seconds to chat about it before the ceremony.

I swear = so help me god, I affirm = so help me.

Not required. Optional

Here are some regs that i think will help out.

AR 601-280 “The Army Retention Program,” Appendix D Paragraph 2k, which states specifically that the reenlisting soldier need not swear to god. Or to USC 512 Title 28 (Revision June 25, 1948 ch. 646, 62 Stat. 925) which clarifies that an oath of affirmation excludes the “so help me god” portion.

AFI 36-2606 (Ch.3, 2. “Detailed Instructions for Completing the DD Forms 4/1 and 4/2”, Table 3.9, Item Number 15 – Confirmation of (Re)enlistment Oath)

It wasn't for my 20 years in the Army

Yes. When you "affirm" instead of "swear" you are acknowledging that you are not "swearing to God." If you state, "I, Cody Voye, do solemnly affirm..." Then the Officer is supposed to just omit that last phrase. Very few Officers administerring the oath catch this, though, so it is best to chat with them before hand.
I, personally, am Christian, but not religious, and for one of my re-ups I had made the conscious decision to leave God out of it, but did NOT follow my own advice. I "affirmed" and the Officer went right ahead with "so help me God." I could have remained silent and stared at him awkwardly, or just went ahead with it. Since I *do* believe in God, I went ahead. But for someone who has a serious objection, it just makes it uncomdortable for everyone.

Thank you my friend SSG(P) (Join to see) for posting. 'So Help Me God' is the last statement in the current U.S. Army enlistment oath. The enlistment oath did not change in U.S. Code no matter what USAF official policy was or is.

Some groups can't swear per their beliefs [they say affirm] while others don't acknowledge any God. They no doubt leave off the last sentence. I don't know if they are authorized to line through the last sentence on their oath of enlistment.

I looed at my enlistment contract from November 1974 and the wording is essentially the same as it was then.

I just checked the current oath for the U.S. Army
I, _____, do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; and that I will obey the orders of the President of the United States and the orders of the officers appointed over me, according to regulations and the Uniform Code of Military Justice. So help me God." (Title 10, US Code; Act of 5 May 1960 replacing the wording first adopted in 1789, with amendment effective 5 October 1962).
https://www.army.mil/values/oath.html

FYI LTC (Join to see) SFC James J. Palmer IV aka "JP4" SFC (Join to see) MSG (Join to see) TSgt Joe C. Maj Marty Hogan

The term GOD is not unique to Christian religions.

An individual, except the President, elected or appointed to an office of honor or profit in the civil service or uniformed services, shall take the following oath: “I, AB, do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter. So help me God.” This section does not affect other oaths required by law.

(Pub. L. 89–554, Sept. 6, 1966, 80 Stat. 424.)

5 U.S. Code § 3331.Oath of office

I see no where in this law that says you drop, So help me God.

No just so help me