During his childhood, Leshem spent his summers at his family's kibbutz, which he characterized as a left-wing community that had positioned itself at the forefront of the effort to achieve Palestinian independence from Israeli occupation.

Subsequently, he spent three years as an Israeli reporter from the West Bank and the Gaza Strip, and was later promoted to the head of the news division at Yediot Ahronot upon writing as an analyst for military affairs.

He oversaw development and production for Israeli TV series such as Arab Labor, the A-word, Traffic Light,[6] and Homeland, an American adaptation of his show Prisoners of War.

[13] Leshem and Amit Cohen struck a long-term development deal with Red Arrow Studios International in 2018, preparing to create a new scripted drama label.

[19] In the summer of 2019, production began on Israel's Valley of Tears,[20] an 8-part mini-series set in the Yom Kippur War, which Leshem co-created with Cohen, Daniel Amsel, Yaron Zilberman, Gal Zaid, and Izhar Has-Lev.

[25] In 2019, he signed with Anonymous Content along with his frequent co-writer Amit Cohen, with whom he'd recently worked on the Hulu series Fertile Crescent, about the Syrian Civil War starring James Purefoy.