Continuity mistake: The 'over-the-top' trench scene in War Horse depicts a single soldier ordered to remain behind and shoot those who have retreated. In one shot he is seen standing guard while, a few feet away, a dead soldier lies in the trench being eaten by CGI rats. Cut away and the same shot of him again, the casualty and the rats are gone.
Continuity mistake: When the horse is caught in the barbed wire between the English and German trenches, the English soldier crosses a swampy area to get to the horse. As he crosses the bridge, it is submerged under the water level, but when the shot changes, the bridge is suddenly out of the water, then back in the water in the following shot.
