Trench warfare was a feature of the first world war seen particularly on the western front. It was so partly because of the very large numbers of men deployed in a constrained geographical area, meaning the entire front could be fortified with trenches and barbed wire.

There were no flanks to turn, and all assaults had to be made frontally. The only way for an attacker to get to grips with the defender was to use artillery to demolish the fortifications and this presented a number of problems, because artillery in the first years of the war was not very good at doing this.

To considerably expand on this, at the beginning of the war, artillery would unlimber on a hill over here and fire using direct line of sight on the enemy on the hill over there. Pretty much in the same way artillery had operated for a long old time, although their breach-loaded recuperating weapons were incomparably more lethal. The big problem with this is that your guns are themselves vulnerable. So better to site your guns behind the hill and shoot over it, in what's known as indirect fire. Essentially you place your guns in defilade and rely on spotters to report and adjust your fall of shot.

You can take this one step further and for each gun, fire a number of rounds at different elevations and see where they fall. Once you have done this, you will have a fair idea of what coordinates to dial in to hit a specific location on map. This is called registering fire.

The main problem is that if you are using a very large number of guns, its going to take a very long time to register them all, and since being shelled is hardly an exercise in the inconspicuous, the enemy are pretty well bound to notice that something bad is going to happen sometime soon in that particular area.

This was an utterly massive problem because it meant that achieving any level of tactical surprise was impossible. The enemy was given plenty of notice to move up reinforcements to shut down any potential break-ins.

So the final development was predicted fire. This meant calibrating each individual gun and each batch of ammunition. Very detailed maps accounting for elevations and depressions were compiled and complex tables of data involving wind-speed, humidity, and temperature were used to compute, with incredible accuracy, exactly what coordinates to dial into a specific gun in a specific location to hit any specified spot on the map. And so finally a degree of tactical surprise could be achieved. Concurrent with the use of predicted fire was the adoption of ‘hurricane bombardments’ which is to say a very high concentration of guns firing a very intense bombardment over a short period of time. For example, at the Somme, the BEF bombardment lasted for 8 days but with relatively few guns per mile of front. For Op Michael, the German bombardment lasted for 5 hours and fired almost 200 shells a second, and at Amiens the BEF bombardment lasted just 45 minutes, the shock being so complete, the Germans did not return fire for a full five minutes after the attackers had left their jumping off points.

We also have the development of counter battery (CB) fire, reached a peak of efficiency. Techniques like flash spotting and sound ranging meant that the vast majority of enemy batteries could be identified, and at the moment of attack, suppressed or annihilated.

Further still was the concept of a barrage – which is to say a curtain of artillery fire which stops the enemy passing through it (it was arguably the German barrage in no mans land on the first day of the Somme that did the most damage, not machine guns). This concept evolved into the creeping barrage – a curtain of fire falling just ahead of the advancing infantry. A hair-raising feat of orchestration that was lethally effective when it worked but infantry that fell behind or ‘lost’ the barrage were almost universally in for a very bad time.

That 'bad time' was somewhat remedied by the devolution of tactics from the battalion to the platoon, along with a vast increase in infantry firepower with the development of the Stokes mortar, grenades, rife grenades, and light machine guns like the Lewis guns.

However the main issue that still remained at the end of the was one of communication. Without reliable, easily portable radios, a commander had no way of knowing what the situation on the ground was without considerable delay. Communication was done by runners, gallopers, carrier pigeons or dogs. By the time messages got to HQ, they would be out of date, and any messages going from HQ to the fighting men would be even more out of date. Later in the war, communications improved with the use of SOS rifle grenades, power buzzers and radio-equipped aircraft, such that barrages could be retarded or advanced as required, or extra fire laid on to support infantry in difficulty or smash up enemy counter-attacks.

However the communications problem was never really solved, meaning that battles had to be fought strictly according to timetable with no deviation from the plan being permissible.

This gave rise to the concept of the 'methodical battle' – a centrally controlled and coordinated combat doctrine. As the French had been in the war for much longer and suffered far greater losses than the British or Americans, this doctrine became very much a feature of the French army in the inter-war period with the aim of saving blood through firepower and planning.

In the context of the battle of France in 1940, methodical battle had the unfortunate side effect of rendering French decision making rather slow.

On the other hand, the Germans had adapted the traditional Prussian doctrine of bewegungskreig (war of movement) to modern developments such as motorisation, aircraft, tanks, and radio and were operating at a considerably faster decision-making pace.

On the strategic level, the overall French war planning was to fortify the direct border between France and Germany – the Maginot Line. The aim of this was not to preclude a German invasion entirely, but to force the Germans to attack through Belgium, as it had in the first war, sweeping through Belgium like a door with its hinges on the Ardennes forest.

As the Ardennes was densely forested with few viable roads, it was reasoned that no significant force could be pushed through in this area without facing a logistical crisis. Initially, German planning matched this assessment and the initial plan did into call for a re-run of 1914.

However, the German war plans were captured when a German aircraft carrying the plans crashed in Belgium. This compelled the Germans to radically review their plans and adopt the 'Manstein Plan' or Fall Gelb (Case Yellow), and incredibly risky proposition that called for the centre of gravity of the German army's motorised and armoured units to attack through the Ardennes and make straight for the Channel coast, while the bulk of its horse-drawn units would advance through Belgium, aiming to encircle the majority of the allied armies.

The plan understandably came up against some resistance from the German high command. It was an extremely high-risk enterprise and entailed the precious Panzer divisions being strung out over considerable distances with exposed flanks. They were extremely vulnerable to counter-attacks, as shown at the battle of Arras on the 21st May where an ad hoc battle group supported mainly by obsolete A11 'Matilda I' tanks seriously threatened 7th Panzer division, prompting the first of the infamous 'stop orders'.

The French however, regarded the captured plans of proof of the validity of their own plans and doubled down on them, committing virtually all of their first rate and mechanised units, as well as the entire British Expeditionary Force into Belgium, leaving the allies with no strategic reserve.

The up-shot of this was that the slow speed of French decision making rendered them constantly on the back foot, and continually reacting to new developments. They were unable to organise a significant counter-attack, having fed their strategic reserve straight in the German trap

Thus, although the French army had some first rate equipment, and numerical superiority, and proved very capable of staging extremely stiff resistance on the tactical level, it never achieved sufficient coordination for these tactical actions to have a significant effect on the operational level.