For most of his life, Bernie Bluestein was not allowed to say anything about what he did during World War II in Western Europe.

Mr. Bluestein was a sophomore at Cleveland School of the Arts in 1943 when he left to join the U.S. Army. He then trained in a secret unit that landed at Normandy, France, shortly after D-Day in June 1944.

“What we did is we attracted the Germans’ attention so that the real units could do whatever they had to do elsewhere,” Mr. Bluestein, age 100, said in an interview.

As a private first class serving in the 603rd Camouflage Engineer Battalion, he created fake shoulder patches that his fellow soldiers wore on their uniforms to impersonate different elements of an infantry division. He also painted truck bumpers to falsely display markings of Army units that were actually elsewhere.

In his final mission, Mr. Bluestein said, the ruses devised by the roughly 360 soldiers of his battalion forced German commanders to spread their defenses thin in eastern France. That, he said, allowed the U.S. Army’s 90th Division — which was actually 10 miles north of the 603rd — to cross the Rhine River with less resistance.

“We saved the lives of about 30,000 soldiers,” Mr. Bluestein said.