JERUSALEM — In the Ukrainian town of Berdichev, Jewish women were forced to swim across a wide river until they drowned. In Telsiai, Lithuania, children were thrown alive into pits filled with their murdered parents. In Liozno, Belarus, Jews were herded into a locked barn where many froze to death.

Holocaust-deniers aside, the world is not ignorant of the systematic Nazi slaughter of some 6 million Jews in World War II. People know of Auschwitz and Bergen-Belsen; many have heard of the tens of thousands shot dead in the Ukrainian ravine of Babi Yar. But little has been known about the hundreds, perhaps thousands, of smaller killing fields across the former Soviet Union where some 1.5 million Jews met their deaths.

That is now changing. Over the past few years, the Yad Vashem Holocaust museum and research center in Israel has been investigating those sites, comparing Soviet, German, local and Jewish accounts, cross-checking numbers and methods. The work, gathered under the title “The Untold Stories,” is far from over. But to honor Holocaust Remembrance Day, which starts this evening, the research is available on the institution’s Web site.

“These are places that have been mostly neglected because they involved smaller towns and villages,” said David Bankier, head of the International Institute for Holocaust Research at Yad Vashem. “In many cases, locals played a key role in the murders, probably by a ratio of 10 locals to every one German. We are trying to understand the man who played soccer with his Jewish neighbor one day and turned to kill him the next. This provides material for research on genocide elsewhere, like in Africa.”

For the purposes of this project, a killing field entails at least 50 people, said the project director, Lea Prais. The killing began in June 1941 with the German invasion of the Soviet Union. From the Baltic republics in the north to the Caucasus in the south, Nazi death squads combed the areas.

The first evidence for what took place was gathered right after the war by Soviet investigating committees largely focused on finding anti-Soviet collaborators.

The new research checks that evidence against German records, diaries and letters of soldiers, as well as accounts by witnesses and the few surviving Jews, some of whom climbed out of pits of corpses.