Rabbi Yitzhak Isaac Halevi Herzog became Chief Rabbi of Eretz Israel (Mandatory Palestine) after Rabbi Abraham Yitzhak Hacohen Kook passed away.
During World War II, Rabbi Herzog was active in the endeavor to rescue European Jews. He met with senior members of the British government, and worked tirelessly to obtain "Certificates" (immigration permits to Eretz Israel) and donations for Jewish refugees in Nazi-occupied Eastern Europe. In his many speeches, he tried to impress upon his audiences the obligation to assist European Jewry. At the Mizrahi conference in Jerusalem in 1944, he declared: "The order of the day is rescue; the rescue of the She'erit Hapleita (surviving remnant)!"
Several months after the end of the war, Rabbi Herzog set out on a journey through Europe, with the aim of reaching and retrieving the thousands of Jewish children who had been hidden with Christian families. Meeting with Heads of State and community leaders, he tried to sway public opinion and recruit influential people. In Poland he met Prime Minister Osóbka-Morawski, and asked him to pass legislation making it mandatory to register Jewish children living in non-Jewish homes. He even met with Pope Pius XII in order to enlist his support in locating the children and returning them to the Jewish fold.
In the course of his travels, Rabbi Herzog visited many places and discovered the enormity of the tragedy and destruction. Entering abandoned Jewish homes, he collected Judaica that had survived the war. The Central Committee of Polish Jews gave him a Torah scroll found under the ruins of the Warsaw ghetto, so that he could bring it to Eretz Israel.
In Germany he went to the DP camps, where he would give Torah lessons infused with words of encouragement and support for the Sheerit Hapleita. He also met with different agencies with the express goal of improving the refugees' material wellbeing.
He made his way back to Eretz Israel on a Polish Red Cross train traveling to Prague, bringing with him 500 orphaned children who had survived the Holocaust. Returning in October 1946, he shared his experiences with different communities, encouraging them to continue to support Holocaust survivors and assist them in reaching the Jewish homeland.