If you're interest in exploring this further, I recommend the book "Strategy" by Hart for a dance through the history of warfare and what works and doesn't.

As for WW1, Germany did defeat Russia. It took America's entry into the war to defeat Germany.

But you want an example. Take WW2. When Hitler allowed his generals to run things, things went well for the German army. When Hitler decided he knew better, he micromanaged the Wehrmacht into defeat and ruin. The Luftwaffe's problems were greatly impeded by Goering making a hash of things, despite his officers pleading with him. Goering would dictate tactics that negated the advantages of the Me-109s in the Battle of Britain. Goering also infamously ordered a literal decimation of his pilots for cowardice, an order that was quietly ignored.

In the naval war, the U-Boot commanders knew that Enigma had been broken and tactics had to change, but Admiral Doenitz knew better and sent them to their doom. Some histories assert that the Germans were clueless about Enigma, but the U-Boot commanders knew the truth.