Have you ever heard of the Battle of Waterloo (1815) where Napoleon Bonaparte was defeated? It is in Belgium, just south of the capital Brussels.
Both covers are Belgian. The stamps are German stamps overprinted 'BELGIEN' for use in German-occupied Belgium.
The first is addressed to a Gunner of the 6th, German Landsturm artillery battery, apparently stationed in Germany Antwerp, Belgium. The stamped address might imply it was a philatelic cover. The family name is of Prussian origin. The item is cancelled at Waterloo. It was sent registered as the label with register number for Waterloo and the German word 'EINSCHREIBEN' indicate.
The second cover appears cancelled at Sclessin that now is a neighbourhood of Liège (Luik).
edit Germany ==> Antwerp, Belgium as address for first cover.
Both of these cancellations are listed in Willy Van Riet's Catalogus der Afstempelingen van de Duitse Bezetting in Belgie 1914-1918 (1982). They are not rare, but carry a slight premium. The catalog lists 1240 town and neighborhood names, along with some railway posts offices.