Treatment of dead soldiers in world war 1?

To my knowledge they usually just left them for the rats. I suppose if there was a period of cease-fire, and they could get to the support trenches they may have been able to give them a simple burial, but the hassle was probably too great. I believe the only time they really ever buried the dead was when a major offensive had succeeded greatly, and they were free to collect their dead. When soldiers died in No-man's land, they were eventually buried under the mud, which created a problem due to the natural build up of gases which wouldn't be able to escape, thus, it was quite common that the aforementioned corpses would actually explode, adding yet more horrors to the war.