Sharjah Fort dates from Imperial days and protected the British garrison from unfriendly tribesmen.
Note the rifle slits which are narrow on the internal side of the walls, but widen out on the external side to provide overlapping arcs of fire.
The left-hand tower is slight forward of the main wall, with rifle slits that cover the gates.
In the 1960s the Fort was owned by International Aeradio (IAL) and provided offices, repair shops, and single accomodation.
When the author was there, the person in charge of IAL Sharjah was Bill Dent.
According to the Sharjah Departure of Culture, Sharjah Fort was partially demolished in 1969, but has since been rebuilt.
See the image at the Sharjah Government Departure of Culture Site
Al Hisn Sharjah Fort
The Arab-style architectural details of the reconstruction jar with those of the Sharjah Fort depicted here.
So too does its supposed history.
Possibly there is some confusion here between the old British-Empire-days Sharjah Fort and the building the Europeans used to refer to as Sharjah Palace.