Veteran Navajo code talkers on were honored in Phoenix on Thursday with a monument commemorating their use of an unbreakable cipher that helped U.S. forces defeat the Japanese in World War Two.

More than 400 Navajo servicemen used an oral code based on their native language to pass messages for the U.S. Marine Corps in the campaign against Japanese troops across the Pacific theater from 1942 to 1945.

Some two dozen veterans were feted in speeches in the state legislature on Thursday and a bronze statue paid for by the Navajo Code Talker Memorial Foundation was inaugurated in a park outside the state capitol.

"It's an honor, it's good, it's something a lot of us never expected Arizona to do," said Keith Little, the president of the Navajo Code Talkers Association.

"The state treated us as second-class citizens ... now we are treasured," he added.

Thousands of Navajo volunteers rushed to enlist in the armed forces following the Japanese air attack on Pearl Harbor in December 1941, many from the sprawling Navajo reservation in northern Arizona.

Around 420 bilingual Navajo speakers were selected by the U.S. Marine Corps and trained as communications specialists, developing a secret code to pass tactical messages in battles fought across the Pacific from 1942 to 1945.

The Navajos' reputation grew as island after island fell, and was sealed during the first two days of the battle for Iwo Jima in 1945, when six Navajo code talkers worked around the clock, sending and receiving more than 800 vital messages without error.

"It's a special day," Little said, speaking of the recognition. "We worked hard for it."

(Reporting by Tim Gaynor; Editing by Eric Beech)