But who is the only undefeated marshall of Napoleon, not Suchet, not Lannes, not Bernadotte, but Davout!
Where did Lannes loose? (don't doubt you, just wondering
Thought Aspern-Essling shouldn't count, as he got his legs smashed and had to leave the battle... he managed to hold back the austrians for a long while there, with a small force. He loved the army and the battlefield and proved himself time and again, despite being wounded many times and often facing great odds. He had a vital role at Friedland, where he held off far greater numbers of Russians long enough for Bonaparte to bring up reinforcements and crush them against the River Alle.
At Aspern-Essling where his advance II Corps held off, against massive odds, the Austrian army while Bonaparte desperately tried to get more troops across the swollen, flooded Danube.
Occupying a strongpoint in the village of Essling, Lannes denied the Austrians for two days. Unfortunately, during the fighting withdrawal he had his legs crushed by a cannonball and, after the amputation of the left one, died of fever.
The army, and Bonaparte himself, wept at the loss.
Concerning Davout... as a young general he was captured by the prussians, but exchanged... the Prussians would certainly regret that... he was also caught by the royal Navy, but again set free.