In August 1944 a unit of SS soldiers massacred over 500 people and burned the northern Tuscan town of Sant'Anna di Stazzema to the ground.
Gauck held a memorial service with the Italian President Georgio Napolitano in a reconciliation effort that followed a diplomatic row involving former German soldiers.
The massacre had been largely forgotten until 20-years-ago when a document was found in Rome sparking a fresh investigation.
In 2004 an Italian court found the surviving eight SS soldiers guilty of crimes against humanity in absentia,but none of them served their sentences and in October 2012 a German court ended its investigation saying there was not enough proof to charge them.
Source: Euronews
