Summary from Wikipedia

After leaving the military, Herzog practised law. In 1972 he was a co-founder of Herzog, Fox & Ne'eman, which would become one of Israel's largest law firms. Between 1975 and 1978 he served as Israel's Permanent Representative to the United Nations, in which capacity he denounced UN General Assembly Resolution 3379—the "Zionism is Racism" resolution—and symbolically tore it up before the assembly. Herzog entered politics in the 1981 elections, winning a Knesset seat as a member of the Alignment. Two years later, in March 1983, he was elected to the largely ceremonial role of President. ...