A week before shooting was due to commence, huge rainstorms blanketed the location, flooding the British trench set. The crew were concerned that this would cause the production to be delayed, but the set had been built so well and so in0-keeping with the way actual trench systems had been constructed--the entire set survived. In fact, the rain only helped to give the set a more textured, "lived-in" feel.
Some of the larger explosions could be heard over 30 kilometres away. Most craters were created prior to shooting but some of the largest ones occurred during filming.
Shot in 21 days.
The film's opening charge sequence took almost two weeks to film. With the 22-day shooting schedule, this meant that the cast and crew would arrive on location in the late morning, shoot a portion of the charge, then transition into shooting the night scenes throughout the evening before wrapping at dawn.
At one point rain on location became so intense that cast and crew were caught in mud up to one foot deep. This meant that moving across even a single set became arduous and time-consuming.