From time to time I play WarThunder, a multiplayer vehicle shooter where you can fly aircraft, drive ground vehicles and direct naval warships from the Inter-War years until the modern times. The focus of that game is on WW2, however (or used to anyway).

In that game, the defensive armament of bomber and attack aircraft is often very lackluster. Now mind you, it is a game, so the depiction of the effectiveness of defensive armament may not at all be accurate to history, for a variety of factors that would be too many to list them all here.

But assuming that its depiction is at least somewhat accurate to history, here is what I noticed:

Most bombers and attack aircraft, particularly those single-engine fighter bombers/attack aircraft/dive bombers and twin-engine heavy fighters/medium bombers/attack aircraft of the Inter-War years and early WW2 era, could only ever fire 1 or 2 defensive machine gun barrels into a given direction. That is barely a threat to an incoming attacker, who would in turn often aim 2, 4, 6 or even 8 machine guns, and sometimes even a few cannons, into the direction of the victim.

One could fly an SBD-2, Pe-2 or He-111 (or similar aircraft, of which there are a lot) and then an attacker would turn up on the rear, your firing arcs barely admit you to fire one MG into their direction, but that would not do enough damage anyway to destroy them and then you get shot down shortly thereafter.

So the question then is: How effective was the defensive armament of WW2 aircraft? Is WarThunder accurate in how it depicts the (lack of) effectiveness of the defensive armament? If it is at least somewhat accurate and defensive armament truly was often not very effective, then why equip the bomber forces with defensive armament at all? It is just dead weight at that point then and removing them might actually be more useful for evading enemy interceptors.

I am aware that the later war bomber models, such as the American B-17 and later series of bombers, which were brimming with defensive armament and would often fly in formations of a hundred planes with overlapping arcs of fire, would have more effective defensive armament, or at least be more effective in using it, which is why my question is particularly aimed at the numerous early-war bomber models which would not fly in such massive formations and would also not brim with defensive armament, such as the numerous SB-2s, Ju 87s, Do-17s, etc... But answers pertaining to the aforementioned bombers and tactics are also ok.

I looked through a lot of the most used/produced attacker, bomber and heavy fighter aircraft types used by each major participant of WW2 and what I noticed was that while barrel count and caliber may vary a lot, one common factor that most aircraft with defensive armament share is that at most only 1 barrel/gun turret faces a given direction. This is due to how the defensive gun positions/turrets were placed among the plane and also partially due to bad firing arcs. So for instance a Ju 87 would have only one gun barrel facing rearward, but so would the He 111. Furthermore both would struggle with being able to fire directly rearward, as the rudder would be in the end. If you ask me, that is not enough to pose a considerable threat to an incoming attacker.

But this brings up the theory that it wasnt important to be a real threat to the enemy, but to just have some sort of deterrence into each direction, as indicated by many of the aforementioned aircraft having one light machine gun barrel facing each direction, which to me does not seem like a real threat, but essentially gives the aircraft a 360° arc of deterrence/threat posing. This would then scare enemy pilots away, even though its no real threat. On the other hand, the massive bomber losses during the war disprove said theory.

Another factor is that some aircraft, particular late war models, would increasingly have 20mm cannons for protection. An answer to the question of whether the calibre of the weapon was important in determining the effectiveness of the defensive armament, or whether it was only about having as many barrels against the enemy as possible, would be good, too.