Conversation so far:
what was the function of the leaning tower of pisa during the world war ii
In World War II, the Allies found out that the Nazis were using the Leaning Tower of Pisa as an observation post.
was the Leaning Tower of Pisa damaged during the war
A US Army Sergeant never ordered a strike on the leaning Tower in order to preserve this piece of art and history.
when was  the Leaning Tower of Pisa completed
The Leaning Tower of Pisa was completed in 1372.
who was the architect of the Leaning Tower of Pisa
A 2001 study seems to indicate Diotisalvi was the original architect of the Leaning Tower of Pisa.

Question: what year did the building begin shifting
Self-contained rewrite: what year did the Leaning Tower of Pisa begin shifting