The "Big Bertha" gun shown in this cartoon refers to the German nicknamed artillery piece that fired a 42cm-diameter shell up to 9.3km from a 5m-long barrel. The gun and its carriage weighed 42,600 kg (47 tons). It was one of the largest artillery pieces ever made, but only saw service in World War One.
The renderings of the weapons and defenses, though humorously depicted, are accurate representations of what was used in both global conflicts.
Released during the height of WW2, the cartoon ends with the patriotic sign, V for victory, popularized by Sir Winston Churchill.