He was a child prodigy and studied without interruption for eighteen hours at a time. When he was nineteen, his grandfather, the Chiddushei HaRim passed away and pressure was exerted on Reb Yehudah Leib to assume the mantle of leadership of the Gerer Chassidim. He felt unworthy however, and instead went to Alexander to study under Rebbe Chanoch Henoch.
After only four years, Rebbe Chanoch Henoch passed away, and then Reb Yehudah Leib was left with no choice but to comply with the wishes of the Chassidim to become the leader of the Ger. Under his guidance and leadership Ger became the largest Chassidic group in Poland. The Sfas Emes, named after his magnum opus, was a proponent of expanding the Chassidic community in Israel, and greatly supported activities to that end. His son, the Emrei Emes, escaped the Nazis, came to Israel and rebuilt Ger, restoring it to its former glory.
Sources: Orthodox Union