<Li> Giovanni di Simone was known to be heavily involved in the completion of the tower, under the direction of Giovanni Pisano, who at the time was master builder of the Opera di Santa Maria Maggiore . Di Simone could be the same Giovanni Pisano who completed the belfry tower . </Li> <P> Galileo Galilei is said to have dropped two cannonballs of different masses from the tower to demonstrate that their speed of descent was independent of their mass . However, the only primary source for this is the biography Racconto istorico della vita di Galileo Galilei (Historical Account of the Life of Galileo Galilei), written by Galileo's secretary Vincenzo Viviani and published in 1717, long after Viviani's death . </P> <P> During World War II, the Allies suspected that the Germans were using the tower as an observation post . A U.S. Army sergeant sent to confirm the presence of German troops in the tower was impressed by the beauty of the cathedral and its campanile, and thus refrained from ordering an artillery strike, sparing it from destruction . </P> <P> Numerous efforts have been made to restore the tower to a vertical orientation or at least keep it from falling over . Most of these efforts failed; some worsened the tilt . On February 27, 1964, the government of Italy requested aid in preventing the tower from toppling . It was, however, considered important to retain the current tilt, due to the role that this element played in promoting the tourism industry of Pisa . </P>

What was the function of the leaning tower of pisa during the world war ii
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