In the summer of 1965, support for the conflict in Vietnam eroded as President Lyndon B. Johnson’s advisors recommended sending hundreds of thousands of servicemen over the course of at least five years to win the war. Troop buildup grew steadily, and on July 28, Johnson ordered the number of ground forces to increase to 125,000 and doubled the number drafted into the military, from 17,000 a month to 35,000.

As more and more young American men were drafted to fight, a new single, "Eve of Destruction" by Barry McGuire, hit the airwaves and drove home a key point of anger in its opening lyrics: Why should men be old enough to be drafted into war and not even old enough to vote?

The eastern world it is explodin'
Violence flarin', bullets loadin'
You're old enough to kill but not for votin'

Released on July 21, 1965, "Eve of Destruction" entered the Billboard charts at #103; by September 25, it had reached #1. In Washington, the government prepared to cap the number of soldiers at 195,000—and young Americans were weeks away from burning their draft cards. The stark realities of the war—and the fear of being drafted—energized a campaign to lower the voting age from 21 to 18.

"You're old enough to kill but not for votin'" was reflected in anti-war protests as "Old Enough to Fight, Old Enough to Vote"—a rallying cry against the draft and for the right of draftees to have some say in their fate. In 1965, 130,991 young men were inducted in the military service; a year later, the number ballooned to 382,010. Many of them were ages 18-20, and thus legally prohibited from voting.

But while the issue burned hotter in the Vietnam era and ultimately led to change, the battle to lower the legal voting age was hardly new.

WATCH: LBJ and Vietnam: In the Eye of the Storm

Push to Lower Voting Age Began in World War II

World War II draft age
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18 and 19-year-old draftees taking their oath upon entering the receiving center at Camp Upton, NY after being drafted into the Service, circa 1943.

The first push to lower the voting age came during World War II. The Selective Training and Service Act of 1940 set the draft age range at 21-35, but in June 1942 President Franklin D. Roosevelt lowered that to 18. Those horrified by the idea that an American could be sent to die for his country before being old enough to participate in its democracy coined a new slogan: "Old Enough to Fight, Old Enough to Vote." This, in turn, prompted West Virginia congressman Jennings Randolph to propose a constitutional amendment to give 18-year-olds the right to vote.

The idea’s time hadn’t come, but that didn't stop a steady push for it. In his 1954 State of the Union address, President Dwight D. Eisenhower urged lawmakers to take up the issue. "For years our citizens between the ages of 18 and 21 have, in time of peril, been summoned to fight for America," Eisenhower said. "They should participate in the political process that produces this fateful summons. I urge Congress to propose to the States a constitutional amendment permitting citizens to vote when they reach the age of 18."

It would take more than a decade—and thousands of deaths in Vietnam, countless anti-war protests, and untold socioeconomic strife—for a true, concerted effort to lower the voting age to manifest. And this time, it couldn't be ignored.

READ MORE: Who Was Involved in the Vietnam War?

Congress vs. Constitution for Changing Voting Age

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Young military recruits of the Vietnam War, circa 1967. 

In May 1965, as troops began landing on Vietnam’s shores, New York Congressman Benjamin S. Rosenthal proposed lowering the voting age to 18. A year later, Vice President Hubert Humphrey pressed for the change, saying it "would have a very good effect on American politics." 

In 1968, Johnson asked Congress to move on the voting age, saying it would be "a national affirmation of faith in our youth." States began passing laws and amending their constitutions to change the voting age. Quickly, it became a question of not if but how the voting age would be lowered—through Congress, or the Constitution.

Senator Edward (Ted) Kennedy, in his March 1970 testimony before the Senate subcommittee on constitutional amendments, said 18 to 20-year-olds' gains in education and service justified having the right to vote. "The well-known proposition—'old enough to fight, old enough to vote'—deserves special mention," Kennedy added. "About 30 percent of our forces in Vietnam are under 21. Over 19,000, or almost half, of those who have died in action there were under 21. Can we really maintain that these young men did not deserve the right to vote?"

But Senator Kennedy argued against an amendment, worried the ratification process would be too slow and further disenfranchise those who would benefit. President Richard Nixon, in April 1970, said he supported the idea of lowering the voting age but only through a constitutional amendment.

The Supreme Court settled the argument.

READ MORE: How Americans Have Voted Through History

26th Amendment Is Ratified in Record Time

26th Amendment ratification
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President Nixon affixing his signature to signify that he was witness to the certification of ratification of the 26th amendment which gives 18-year-olds the right to vote, on July 5, 1971.

On June 22, 1970, Nixon signed the Voting Rights Act of 1970, which extended the 1965 Voting Rights Act and included a provision that lowered the voting age. Its constitutionality was quickly challenged, and in Oregon v. Mitchell the Court deemed unconstitutional lowering the voting age to 18 in state and local elections but affirmed that change for federal elections. An amendment was now all but necessary to reconcile the inconsistency.

The 26th Amendment, ensuring the "right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age," passed the Senate 94-0 on March 10 and, 13 days later, the House of Representatives 401-19. It was ratified by three-fourths of the states on July 1. In all, ratification took 100 days—faster than any amendment in US history—and minted 11 million new voters.

Nixon certified the amendment on July 5 in the East Room of the White House, in front of the 500-member choral group Young Americans in Concert. He even randomly selected three 18-year-old members to sign the amendment as witnesses.

"For more than 20 years, I have advocated the 18-year-old vote. I heartily congratulate our young citizens on having gained this right," Nixon said upon ratification. "I urge them to honor this right by exercising it—by registering and voting in each election."