JERUSALEM (AP) — The chairman of Israel's Yad Vashem Holocaust Museum and Memorial said Sunday he will be stepping down after 27 years.

Avner Shalev, 81, said in a letter to Yad Vashem employees that he made the decision to leave the position after nearly three decades following “thorough self-examination.” He said was stepping down by the end of year and gave no further details on his reasons for leaving.

Shalev guided a period of dramatic transformation at one of the world's foremost Holocaust remembrance institutions. During his tenure, the site expanded to include a sleek new museum, a centerpiece that draws hundreds of thousands of visitors a year, and the solemn Hall of Names, a collection of 4.8 million names of Holocaust victims, which is a mainstay during visits of foreign dignitaries to Israel.

He also oversaw the creation of an international school for Holocaust studies and an institute for Holocaust research.

According to his letter, a successor has not been designated.

Yad Vashem is an almost sacred institution in Israel, where students, soldiers and company outings tour regularly and where the country holds its annual Holocaust remembrance day ceremony.

Still, during Shalev's term, it has weighed in on a number of controversies.

In 2015, Yad Vashem challenged the accuracy of a claim by Prime Minister Benjamin Netanyahu suggesting that a World War II-era Palestinian leader persuaded the Nazis to adopt their Final Solution to exterminate 6 million Jews.

It lambasted an Israeli-Polish compromise over a Polish Holocaust hate speech law, saying a joint statement by the countries' prime ministers contained “grave errors and deceptions” over Poland's role in the Holocaust.

It also came out against a government plan in 2018 to deport tens of thousands of African migrants, saying it saw the issue as a “national and international challenge that requires empathy, compassion and mercy."

"The experience of the Jewish people over generations heightens this obligation,” it said.