"Growing up in Silicon Valley, where everyone's thinking about the future, what's the next big thing, I found myself wanting to go back to the past," Retelas said. "Because I feel like I don't know how to answer the questions of the future until I learn more about where I came from."

He directed his first documentary, Eleven, in 2014, built around the journal he had found. His second, Sundown to Eleven, followed Richard "Dick" Miralles, the last surviving member of Air Group 11, in his mission to honor his fallen comrades. Miralles passed away on Nov 13 last year, at age 101. In keeping with his dying request, Retelas released the film for free on You-Tube on Pearl Harbor Day, Dec 7.

But even as he completed that work, Retelas was being pulled across the Pacific, and toward a viewpoint he realized he did not yet grasp.

"I wanted to understand the other side, instead of just getting the American perspective of the Pacific War," he said. "Now, I want to know who it affected on the other side of the world."

In April 1942, just four months after Japan attacked Pearl Harbor, US President Franklin Roosevelt ordered a retaliatory strike on the Japanese home islands.

The attack, involving 80 men in 16 Army B-25 bombers, was planned and led by Lieutenant Colonel James Doolittle.

The mission was nearly suicidal in its ambition: Because the aircraft carrier USS Hornet was not close enough to Japan for the bombers to make the return trip, they would bomb Tokyo and other Japanese cities, then pray they made it safely to allied China before they ran out of fuel.

Eighty men bailed out or crash-landed across the provinces of Zhejiang, Jiangxi, Fujian and Anhui. Chinese farmers, villagers and townspeople took them into their homes, fed them and helped them escape until 64 of the 80 made it to safety.

Japanese forces, enraged that the local population had sheltered US forces, swept through the region. An estimated 250,000 Chinese civilians were killed in Zhejiang-Jiangxi campaign in retaliation by Japan for the Doolittle Raid, according to multiple sources.

In the United States, the Doolittle Raid is remembered as a daring act of national defiance. The role of China, and the sacrifice made by ordinary Chinese people, are often overlooked.

"For American students and young people, it's not really well known," Retelas said of the Pacific War broadly.