After the sudden death of his father Gebran Tueni, Ghassan, just 22 at the time, returned to Lebanon to continue publishing "An Nahar". He became editor-in-chief and publisher of the paper from 1947 to 1999, and from 2003 until his death. He was imprisoned in the 1940s for his objections to censorship. Committed to his father's work, Ghassan developed a new team of journalists, modernising the editorial content and its production. "An Nahar" was at the time Lebanon's foremost daily and the Arab world's most credible and authoritative newspaper.