Forced to emigrate, Rutenberg settled in Italy.
Away from politics, he concentrated on hydraulic engineering.
Pondering on specific Jewish problems, he became convinced that the solution was to establish a national home for the Jewish people.

After World War I broke out, the Zionist movement mainly supported the Entente Powers.
Rutenberg set the goal to create a Jewish armed force to fight for the Land of Israel.
He visited European capitals, met prominent politicians and Zionist leaders, and finally joined the efforts of Jabotinsky and Trumpeldor to set up the Jewish Legion.
In May 1915, on Jabotinsky’s approval, Rutenberg travelled to the United States to promote this idea among the American Jewry.

He found strong support among Jewish organizations in New York City.
Rutenberg endorsed the labour party (Poalei Zion) and cooperated with David Ben-Gurion, Itzhak Ben-Zvi, and Ber Borochov.
Together with Chaim Zhitlowsky, he founded the American Jewish Congress.
At the same time, Rutenberg published his book The National Revival of the Jewish People under the pseudonym Pinhas Ben-Ami (in Hebrew: my people’s son).

While in the US, Rutenberg managed to complete a detailed design for utilizing the Land of Israel's hydraulic resources for irrigation and electrical power production, which was his long-time dream.
Forced to emigrate, Rutenberg settled in Italy. Away from politics, he concentrated on hydraulic engineering. Pondering on specific Jewish problems, he became convinced that the solution was to establish a national home for the Jewish people.
After World War I broke out, the Zionist movement mainly supported the Entente Powers. Rutenberg set the goal to create a Jewish armed force to fight for the Land of Israel. He visited European capitals, met prominent politicians and Zionist leaders, and finally joined the efforts of Jabotinsky and Trumpeldor to set up the Jewish Legion. In May 1915, on Jabotinsky’s approval, Rutenberg travelled to the United States to promote this idea among the American Jewry.
He found strong support among Jewish organizations in New York City. Rutenberg endorsed the labour party (Poalei Zion) and cooperated with David Ben-Gurion, Itzhak Ben-Zvi, and Ber Borochov. Together with Chaim Zhitlowsky, he founded the American Jewish Congress. At the same time, Rutenberg published his book The National Revival of the Jewish People under the pseudonym Pinhas Ben-Ami (in Hebrew: my people’s son).
While in the US, Rutenberg managed to complete a detailed design for utilizing the Land of Israel's hydraulic resources for irrigation and electrical power production, which was his long-time dream.
Pinhas Rutenberg