Souain-Perthes-lès-Hurlus [swɛ̃.pɛʁt.lɛz‿yʁ.ly] is a commune in the Marne department in north-eastern France.

On 9 December 1915 at Souain, a former battlefield with rough terrain and trenches, and in the presence of General Philippe Pétain, a prototype armoured vehicle motorized with a Baby Holt caterpillar was successfully tested.

The village is the site of the Monument de la Légion Etrangère, an ossuary with 130 bodies of légionnaires from the 1st and 2nd Régiment Etrangers, who fell at the French offensive in Champagne, in September 1915.

The monument ossuaire was erected in 1920 by William Farnsworth, father of Harvard alumnus Henry Farnsworth, a young American university student who had enlisted in the French Foreign Legion on 5 January 1915 and was killed 28 September 1915.

[6] [7][8] The war had devastated the region, making construction very difficult.