When Blake and Schofield walk through No Man's Land, their boots become caked in mud, but after they go through the German bunker and come out of the other side, the mud is gone despite them not cleaning it off.
Blake and Schofield are seen charging their rifles using stripper clips before setting out. The rifles are never seen to be reloaded again, despite having been discharged multiple times. The maximum capacity of the Lee-Enfield is 10 cartridges.
When the soldiers go over the top, a few are seen charging ahead of the others, but they were not seen coming out of the trenches.
British trenches did not use long straight sections. Instead they used a traverse system of short fire trenches linked by traverses to minimize damage from a direct artillery hit in the trench system.
A bomb going off a couple feet away from the two soldiers inside a small underground bunker would deafen them, probably permanently. It doesn't affect them at all, not even a ringing in their ears.
An officer transporting the detachment clearly refers to the "casual truck." Casuals were soldiers who had been separated from their units; the men in the truck are being sent up the line to rejoin their units. As such, it would be entirely plausible to have Sikhs riding in the truck with British soldiers.
In 1917, British troops did not use human wave tactics as depicted in the attack at the end. By the end of 1916 the British army had been sufficiently trained, and attacks used squad and combined arms tactics.
The strategic German retreat in early 1917 was not an attempt to lure British unites into a trap - it was an attempt to shorten their lines after taking almost a million casualties during Verdun and the Somme.
Lance Corporal Schofield at one stage was washed down some rapids. When he finally delivers the message from the General, it is completely readable though it was submerged in the water, and the ink of the time would have totally run down and been unreadable. However, Schofield had placed the letter into a metal box with his photographs, and this box might have been sufficiently watertight to keep the contents dry during the time he was submerged.
Near the end of the film 'No Man's Land' the soldiers charge through to get to the German trenches is a grassy meadow. In reality 'No Man's Land' was all muddy and full of craters and littered with bodies and debris. However, this area is a new front line, which means there had been no battles in the area yet and the new No Man's Land was untouched.
After the incident at the farmhouse the barn is fully engulfed in fire from the plane crash, however moments later when Schofield and the officer are walking to the truck the barn comes into view in the background with no fire or smoke visible.
After the whistle to go "over the top" as Schofield leaves the trenches in the climactic scene in his desperate bid to reach Colonel Mackenzie, three (seemingly unarmed) charging British soldiers are seen on the left of the frame. It would have been impossible for them to reach that position without starting their attack alone well before the whistle, and it likely was mistakenly added as a special effect.
When the two soldiers finally reach the German entrenchments and find them abandoned, it appears as if the departing Germans swept and vacuumed the trenches upon their departure. No empty ammunition boxes, no waste, no paper, just cleanly swept and the retreating German army would certainly not have cleaned the area.
Upon leaving the German dugout, Blake checks his compass and states that they will move out on a SE bearing. But as they move it can be seen from their midday shadows that the sun is directly behind them, which could not happen if they were moving to the SE.
When Schofield goes over the waterfall, the water at the bottom becomes calm within five or ten feet, when, in reality, the water would be rough for a longer distance. It's possible this may have been one of the hidden cuts in the film.
When the two main characters start walking south-east their shadows are in front of them, implying that the sun is in the north-west. The sun can never be in the north-west in the northern hemisphere.
In the 26th minute as Schofield and Blake are behind enemy line trenches, one hears loons. There are no loons in France, and even if there were ,they would not likely have been there during a prolonged, violent and noisy war.
When crossing no man's land Schofield cuts his hand on barbed wire and shortly afterwards plunges the same hand into a rotting corpse. Knowing he just increased his chances of infection he should have immediately flushed it with water and put disinfectant on it. (They had been given adequate supplies) Instead, he waits and then merely wraps his hand, thereby keeping the germs in his hand.
Since this movie was set in Europe, and all the soldiers are British and German, they should be utilizing metric terms like meters and kilometers (klicks for short). However, we only hear American imperial measurement terms like miles and yards.
The British used the Imperial system of measurement at the time of the first and indeed second world war.
Obvious green screen use (shadows/depth of field don't match) when slowly panning across soldiers during the song near the end of the movie.
A ditched British Mark II tank appears briefly. The film is set on April 6th, 1917. Tanks were not used in the area where the film is set until April 9th, 1917.
Almost all of the British officers are wearing the "asparagus braid" (rank on sleeves) style jackets with shirt and tie. This would be correct for the start of WW1, but by 1917 almost all front line officers would have switched to a high collar jacket with rank on the shoulders, as this made them less obvious to snipers. This change had been made unofficially by many individual officers earlier in the war (simply by adding officer's rank to the shoulders of an enlisted issue jacket) but by 1917 this was officially allowed as an alternative option, which nearly all front line officers took.
When Schofield and the men in the truck are pushing the stuck truck out of the mud hole, you can clearly see a clean bright board (about 12" x 8') laid out for them to stand on. Someone mentions "we need some work and they are standing on a piece that would be perfect to do the job." It is gone in the next shot.
Right after speaking to the major outside the Colonel's command post, two soldiers on the right hold their rifles inclined to the camera. One can clearly see a flat metal surface where there should be the rifle bore hole, indicating they are movie props.
Reaching Croisilles from Écoust-Saint-Mein requires crossing a river, La Sensée. This river is a narrow stream though, without any rapids, let alone waterfalls, given the flatness of the Arras plain.
The abandoned artillery position seen in the German section is much too close, situated just behind the German trenches. During trench warfare on the western front, the artillery was placed a few miles behind the trenches on both sides so that the guns would have a better distance to fire at the enemy. For example if the guns fired too close to the enemy lines then the artillery could miss the trenches as the guns were designed to fire for several miles. By firing from several miles, the artillery would have had a better chance on killing the enemy with plunging fire dropped into the trenches while also being safe from trench raids.
Croisilles is not to the southeast from Écoust-Saint-Mein, but to the northwest.
Although the phone lines had been cut, the RFC were flying over the whole area as they had taken aerial shots of the new German Lines so it would have been far simpler to put the message in a canister with ribbons attached and dropped by a plane onto the troops. They had enough time to make a number of drops to ensure success instead of just sending 2 men who may or may not get through. There was even enough space behind and around the Devon's position to safely land and take off again in a plane from that era.
According to General Erinmore, the Germans had left their respective trenches, which was proven correct. That being the case, it was pointless for the British to be on the firing line waiting for the signal to attack or defend. Apparently, during trench warfare, the British would actually 'steal' the German trenches as their method of moving forward.
During a meeting with General Erinmore inside a bunker, both Schofield and Blake keep their helmets on. When meeting a superior officer indoors, soldiers must remove their hats or helmets as it a traditional military rule.
General Erinmore does not inform Blake and Schofield what to do once the mission is accomplished. He should have told them to either stay at their destination or journey back to their own battalion.
Blake refers to picking cherries in May. Cherries are usually harvested in June at the earliest in England.
The protagonists are too careless to be experienced front line soldiers. For example, at the first German trench, they just jump out of cover even though the trench could have held a large number of enemy troops. When they come across the abandoned farm house, they just trot toward it in plain view and broad daylight down a sloping meadow. Even a single enemy soldier in there could have killed them easily.
When the corporals enter the first German trench, they find a bucket of hot embers prompting one to say to the other, "They [the Germans] are not long gone", implying it has been a matter of hours. However, embers in a bucket like that shown can stay hot for 3 or 4 days as they are insulated by the covering ash.