All this above is what makes the horrible clatter sound on say pre-99 powerstrokes, and pre-duramax for sure (I work on the dinosaurs in the army).
All the pressure and force from the high compression ration and the 1,000 plus degree temps igniting the fuel literally explodes thereby "forcing" the piston back down to complete the cycle. Most modern diesels are equipped with a "wait to start" light that allows the glow plugs to warm up prior to starting the engine via glow plug controller and attempting to make the starting process easier. (I have never had an easy time starting our 6.2/6.5 fleet on a bitter cold morning)
1994 sun faded (New Mexico/Texas truck) maroon, regular cab, 2.3 5 speed & 3.73's. Bought w/ 227k and climbing.