Worth looking at issues raised by the war on the eastern front (Axis forces), and the Korean War (UN Forces), and how units of some countries had limited capablity, due to either poor equipment or training, or both.
Frequently in Russia the Germans provided the punch while the weaker Axis forces protected the (often dangerously exposed) flanks. Once the Russians worked this out and exploited it, it was devastating for the Axis forces.
In Korea (really the first truly multinational army), it was often the South Korean forces which folded very swiftly leaving the flanks of the much more capable forces exposed, leading to the retreat of the UN forces. Even the Battle of Imjin River, where the line was held very effectively to allow time for a controlled withdrawal, exposed problems with C2, with the British ability to understate the seriousness of the situation leading to the loss of the Glosters.