Each of the Army Corps areas conducted maneuvers in 1940-41. The Louisiana maneuvers was in the public conscientiousness for several reasons, not the least of which was the photo coverage in Life magazine. The image was probably taken during the period of these large maneuvers. Without caption information it's impossible to be certain when the image was captured.

I concur with the assessment of the poor cover provided by wood and hay, but the soldiers were instructed not to damage any public or private property, and the umpires would have given these soldiers credit for cover and concealment.

The image reminds me of the poem "The Charge of the Mule Brigade", based on Tennyson's "Charge of the Light Brigade", and an actual incident during the Civil War when Confederate troops attacked a Federal supply depot, and were "routed" by mules that broke loose and were taken for Federal cavalry.