Final answer:
The character Leiningen, from Carl Stephenson's story, pumped water, and possibly petrol, into his defense ditches against an invasion of army ants. Dr. LeVasseur seems to be from a different context and is unrelated. For an accurate answer, clarification on the source material is needed.
Step-by-step explanation:
The question refers to a situation from a story where Leiningen, not Dr. LeVasseur, is likely the character in question.
In literature, especially in the short story "Leiningen Versus the Ants" by Carl Stephenson, Leiningen is a plantation owner who pumps water into his defensive ditches to protect his estate from an advancing army of army ants. In the context provided, the narrative seems to involve Dr. LeVasseur during a wartime scenario, which is unrelated to the story of Leiningen.
Therefore, to provide an accurate answer, it is necessary to clarify the source material. However, assuming the question mistakenly references Leiningen, he pumped water, possibly mixed with petrol, into the trenches to create a barrier against the ants. This action is a central strategy in his defense of the plantation in Stephenson's story.