- Mons, first British death -
After Liege, it is the turn of Mons on the French border, scene of a do-or-die rearguard action by the first British troops committed to the war as London and Paris scrambled to prevent a German breakthrough in late August.
Prince William, his wife Kate, along with Prince Harry and Prime Minister David Cameron will lead the tributes in Mons where the first British soldier died.
It was here, too, that the last British soldier was killed on November 11, 1918, the very day of the Armistice that ended hostilities after four bloody years.
The Mons ceremony will focus on the small military cemetery of St Symphorien, where 229 Commonwealth and 284 German soldiers were buried together in a gesture of reconciliation even as the fighting raged.
St Symphorien "is a uniquely fitting place for us to gather in a spirit of common remembrance," the Commonwealth War Graves Commission said.
"On land donated by a Belgian, in a cemetery first built by the German army and now cared for by the CWGC, the fallen from both sides of the conflict lie together at peace. Today we remember them all."
Britain, which declared war on Germany on August 4, 1914, will on Monday hold its own World War I commemorations, including a parade of 40 cars from the 1900s and a candlelight vigil in Westminster Abbey.