Ramban on Shelach: Who Sent the Spies and Why?

We examine the question of motivation of the Jews, Moshe and God in sending the spies. The questionis framed by discrepancies between the accounts in Bemidbar and Devarim.

Was it wrong to want to investigate scout out the land? Was God merely enabling them?  Were they asking for military preparation purposes or for a general feeling of encouragement?

Ramban seems to think that sending the spies was initially a good thing. What accounts for the negative portrayal of the request to scout out the land in Devarim? The attitudes may have changed- at the beginning, the people had the right mindset, but then something shifted.