Johnnie A. Jones Sr. was 24 years old and a future civil rights lawyer not yet graduated from college when he landed on the beaches of Normandy in the D-Day invasion of 1944.

He nearly died before his ship reached the shore, when the explosion of a mine sent him flying “sky high into the air,” he recalled, and onto an upper deck. He again almost died when he came under German sniper fire on Omaha Beach.

“I remember it all,” Mr. Jones told a Veterans Affairs publication last year. “Sometimes reminiscing is a terrible thing. … I lay down at night, and as soon as I close my eyes, I relive the whole D-Day invasion.”

When Mr. Jones returned home to Louisiana, he was greeted not with a hero’s welcome, but rather with all the indignities of segregation in the Jim Crow South.

Riding a bus with fellow U.S. service members, Mr. Jones, who was African American, was forced to sit in the back of the coach. He was driving to New Orleans to have shrapnel removed from his neck when a White police officer, entirely unprovoked, pulled him over and began assaulting him.ADVERTISING

“He knocked me down and started kicking me,” Mr. Jones said. “Things weren’t right. ‘Separate but equal’ was unconstitutional, and I wanted to fight it and make it better.”

Mr. Jones did so by enrolling in law school and becoming a lawyer in the early years of the civil rights movement. He was 102 when he died on April 23 at a veterans’ home in Jackson, La. A goddaughter, Mada McDonald, confirmed his death but did not cite a cause.

Mr. Jones was credited with fighting legal battles on multiple fronts of the movement for racial equality.

He worked with voter leagues and with civil rights organizations, including the NAACP and the Congress of Racial Equality (CORE). He assisted demonstrators who participated in lunch-counter sit-ins. Twice his car was bombed, he said.

After the 1954 Supreme Court ruling in Brown v. Board of Education, which outlawed segregation in public schools, he helped accompany about 30 Black children to a White elementary school in Baton Rouge, historian Adam Fairclough wrote in the volume “Race and Democracy: The Civil Rights Struggle in Louisiana, 1915-1972.”

But Mr. Jones played perhaps his most significant role in the 1953 Baton Rouge bus boycott, a long-overlooked event that helped inspire the landmark boycott two years later in Montgomery, Ala., prompted by the arrest of Rosa Parks.

Mr. Jones was only two weeks out of law school in June 1953 when the Rev. T.J. Jemison, a founding member of the Southern Christian Leadership Conference, invited him to represent the organizers of the effort in Baton Rouge.

“I told him, ‘That’s an awfully big suit to fill,’” Mr. Jones recalled to a reporter in 2015. “But he said, ‘Nonsense, Brother Jones, you can do it.’”

The Baton Rouge demonstration was touched off when Martha White, an African American housekeeper, ignited a controversy by taking a seat in a section of a public bus reserved for White riders. During the eight-day boycott that followed, activists organized car pools that allowed participants to travel to and from work without riding city buses. Eighty percent of the city’s bus ridership at the time was African American.

The boycott ended with the partial desegregation of city buses, with the front two rows of seats reserved for White people and the last two rows for Black people. While some protesters had hoped for a more dramatic outcome, historians today describe the Baton Rouge boycott as a prototype of others to come.

The Rev. Martin Luther King Jr. consulted with organizers in Baton Rouge before organizing the Montgomery boycott, which lasted 382 days and ended with a Supreme Court ruling desegregating the Montgomery transit system.

“Almost unnoticed at the time,” the Baton Rouge protest “was a direct precursor of the Montgomery bus boycott,” Fairclough wrote, “and an event of major significance in the evolution of the civil rights movement.”

Johnnie Anderson Jones was born Nov. 30, 1919, in Laurel Hill, La., and was raised on a plantation where his parents farmed. He attended a two-room schoolhouse and became interested in the law, he said, when a teacher gave him a book by Charles Evans Hughes, then the chief justice of the United States.