The first use of the new type of weapon — the tank — took place on the Somme on September 15, 1916, and, as you know, was accompanied by a great deal of secrecy. We should admit that the British fully managed to make use of the surprise effect. However, the tank soon became not only a regular subject of battle reports, but also an attribute of front-line folklore and propaganda.
The first tanks appeared on postcards immediately after they were used for the first time at the front. In the beginning they had improbable outlines, but after two or three months, drawings with quite recognizable «rhombuses» became widespread.