It would depend on the individual officers. Obviously in Nazi Germany, there was no formal consensus on the war having been lost. The fact that the Ardennes Offensive (The Battle of the Bulge) went ahead in december 1944, and German marshals were still drawing up new plans in the Battle of Berlin, show that the Germany military was still, if nothing else, willing to continue the fight.

Since there is no formal documentation about the entire German military realising the war was lost, there are a number of turning points at which various individual commanders may have realised that things were not going their way.

In 1943, Admiral Donitz was quoted as having said "Losses in the atlantic have reached intolerable levels."

Erwin Rommel said, in 1944, that the defences prepared on the french coastline were entirely inadequate to repel any allied landing, and that if a landing succeeded, Germany would not win on the land.

Erich von Manstein was an influential German commander at the battle of Kursk, following which his disagreements with Hitler about the war led to his dismissal.

By 1943, a fair few commanders were very disillusioned by German chances, particularly against the USSR. The loss at Kursk certainly fuelled this attitude.

As another famous example, there were supposed orders from Hitler to destroy Paris if "occupation troops" approached the city. But Gen. von Choltitz, commander of Paris, knew that destroying the city was of no strategic value, and refused to execute the order. Sappers had prepared every historical site and bridge with explosives on military orders, but the order from von Choltitz to blow them up was never given.

He and his men surrendered to the Allies on 25 September 1944.

One of the first points where the German High Command realized that the war would no longer be in their favor was after the failure to take Moscow in Operation Typhoon. In their failure to achieve the strategic goal of surrounding and dominating Moscow in December of 1941 the High Command soon came to the realization that they would have to fight a battle not simply to win the war, but to maintain their position on the Eastern Front.

After the Wehrmacht stalled outside the edges of Moscow in the face of fanatical and reinforced Soviet resistance - for a variety of reasons: the onset of winter, poor logistics, delays after priority was given to encirclement at Kiev, and massive soviet reserves. The Wehrmacht not only saw the failure of their offensive, but a massive Soviet counter offensive that threatened their entire position all along the Eastern Front. Massive reserves brought in from Siberia after Richard Sorge informed Stalin that the Japanese would not attack through Mongolia gave a boost to Zhukov in his ability to defend and counter the German offensive. The rapid advance of the Soviet counter offensive through the Germans into disarray as thousands of units had to retreat chaotically in the frigid Russian winter to form proper defensive lines and reestablish broken communication with command. As the situation normalized the Germans realized to their horror that no matter how many divisions and armored formations they had surrounded and destroyed, the Soviets still had fresh reserves ready to push them back after their massive gains.

Many in the High command after this point soon realized that they were about to have to fight a long, bloody, and protracted conflict they were ill prepared for. The entirety of the German plan for the invasion of Russia - and all of their previous campaigns - relied on tactical surprise and encirclement. They needed to destroy and demoralize the Red Army as quickly and as rapidly as they could muster. The Wehrmacht had already expended massive amounts of casualties in the run up to Operation Typhoon - already in the hundreds of thousands by this time. They had no amount of reserves to be able to sustain such a large and precarious position along the massive Eastern frontier.

Commanders became cognizant of this situation and realized that they had one more chance in order to truly knock out the Red Army's fighting capability - which would culminate in Operation Blue - Army Group South's attempt to both sever the Volga and take the Caucasus oilfields at Maikop, Grozny, and Baku. These events would culminate in the incomparably blood Battle of Stalingrad that would turn the fortunes of the Red Army and put them on the offensive against the Wehrmacht on the Eastern Front