Your presence is mandatory : a novel / Sasha Vasilyuk.

Enhanced descriptions from Syndetics:

A riveting debut novel, based on real events, about a World War II veteran with a secret that could land him in the Gulag, and his family who are forced to live in the shadow of all he has not told them.

Ukraine, 2007. Yefim Shulman, husband, grandfather and war veteran, was beloved by his family and his coworkers. But in the days after his death, his widow Nina finds a letter to the KGB in his briefcase. Yefim had a lifelong secret, and his confession forces them to reassess the man they thought they knew and the country he had defended.

In 1941, Yefim is a young artillerist on the border between the Soviet Union and Germany, eager to defend his country and his large Jewish family against Hitler's forces. But surviving the war requires sacrifices Yefim never imagined-and even when the war ends, his fight isn't over. He must conceal his choices from the KGB and from his family.

Spanning seven decades between World War II and the current Russia-Ukraine conflict, Your Presence Is Mandatory traces the effect Yefim's coverup had on the lives of Nina, their two children and grandchildren. In the process, Sasha Vasilyuk shines a light on one family caught between two totalitarian regimes, and the grace they find in the course of their survival.