the Middle East, Central Asia and South America, most particularly the construction of the Trans-Iranian Railway, in which he participated as a Sector Engineer.
[1] During the Second World War (1939–1941 and 1943–1946) Gruner was in charge of several military construction works in his homeland.
As the responsible for the Public Works Department, Gruner directed the construction of power plants, railways and irrigation systems in India, Pakistan, Syria, Sudan and Uruguay.
In 1976 he was asked by a subcommittee of the United Nations General Assembly to survey the damage caused to the Syrian town of Quneitra during the Israel-Syrian wars in 1967 and in 1973.
Gruner worked with team of Swiss engineers and military experts, who lived in the town for four months and examined every recognizable structure.