I don't believe we expected the drawn out resistance we got in post WWII Germany either.
Stephen E. Ambrose wrote in Citizen Soldiers: The U.S. Army in Europe from June 7, 1944 to May 8, 1945 that the planners for Operation OVERLORD looked at the terrain of Normandy and saw lots and lots of hedges.
They assumed that the hedges that dominated the Norman landscape were like the small hedges they saw in Britain. Not so; these were hedgerows, tall and forbidding hedges that had been around since the time of Caesar's conquest of Gallia. The Wehrmacht had planned to use these formidable obstacles to defend Normandy if the Allies had landed there successfully. This one mistake led to Allied forces landing in Normandy without proper means to crash through the hedgerows. Several thousand Americans were killed in June of 1944 before this problem was solved by some innovative NCO's.
No one gets war right. Ever.
What matters is who wins.
Be Seeing You,
Chris
Which is why I think we did expect resistance. There's always resistance - knowing the exact form it will take is the problem.