He worked to help Soviet Jews immigrate to Israel.
Explanation;
-A major contribution of Natan Sharansky was that he worked to help Soviet Jews immigrate to Israel.
-Natan Sharansky was an Israeli politician, human rights activist and author who, as a refusenik in the Soviet Union during the 1970s and 1980s, spent nine years in Soviet prisons. Through his efforts he helped the Soviet Jews to immigrate to Israel.