A recent news item about Jerusalem's Mayor Uri Lupolianski's asking the Turkish government to return to Israel the ancient Siloam inscription called attention to the history of the tablet.
In Divrei Hayamim II (32:2-3) it is recorded that King Chizkiyahu ordered the stopping up of the springs around Jerusalem, which were the source of water for the city, in order to deprive the invading Assyrian army of Sancherib from making use of them. To make those waters still available for his people "he brought them straight down to the west side of the City of David" (ibid. 32:30).
Historians say that this refers to the 450-meter long tunnel that the king's workers hollowed out of bedrock. The Siloam inscription, named for the spring whose waters flowed through this tunnel, records the dramatic moment when the two teams of excavators that dug in opposite directions met to celebrate the completion of the project.
The Siloam inscription was discovered in 1880 and taken by the Ottoman rulers to an Istanbul museum. Mayor Lupolianski asked the Turkish ambassador to Israel to arrange for the return of the historic tablet as a gesture of good will between allies. It should be noted that while the stopping up of the springs may have been a clever military strategy, Chizkiyahu was criticized by the Sages for taking such a drastic step rather than relying on G-d's promise (Melachim II, 19:34) that "I will defend the city to save it." (Pesachim 56a)