a line of stone monuments
... that a line of stone monuments marks the limit of the German advance on the Western Front in 1918?
... that <b id="mwCB8"><a href="./Western_Front_demarcation_stones" id="mwCCA" rel="mw:WikiLink" title="Western Front demarcation stones">a line of stone monuments</a></b> <i id="mwCCE">(example pictured)</i> marks the limit of the German advance on the <a href="./Western_Front_(World_War_I)" id="mwCCI" rel="mw:WikiLink" title="Western Front (World War I)">Western Front</a> in 1918?