The Polish army launched a major counter-attack against the German invasion, which led to the largest and most bloody single battle of the Polish campaign, the Battle of Bzura. It saw the last full-scale use of cavalry as a battlefield arm, but, contrary to legend, the Polish cavalry performed effectively on the German flanks. The spurious image of horsemen charging tanks was an appealing one for German propagandists, keen to trumpet German superiority in all things. The thrust to the west of Warsaw did achieve some initial success but was quickly pushed back. The Poles lost some 20,000 men and the Germans 8,000. The Polish army fell back towards Warsaw, but the city was already practically surrounded. The undeclared war between Japan and the Soviet Union in the east, which had reached its most intense in the full-scale battle of Nomonhan on the Khalkin Gol came to an end with s signed cease-fire. The Soviet victory at Nomonhan had played some part in persuading Stalin to