Rabbi Yitzchok Zelig Morgenstern, the Sokolover Rebbe
Chassidic Rebbes Between the Centuries
From the Biography Series

After the death of the Kotzker Rebbe, his Chassidim split and followed many rebbes, but the one who most closely resembled the fiery original was his great-grandson, the Sokolover Rebbe. Sought out by many, he was a self-taught medical expert and political diplomat, but most surprising of all was his outspoken support of the resettlement of the Land of Israel.