What did Ezra proclaim at the Ahava Canal instead of asking the king for a military escort?

Answer: A fast

Ashamed to ask for soldiers after telling the king that God's hand protects those who seek Him, Ezra proclaimed a fast and prayed.

“And there by the Ahava Canal I proclaimed a fast, so that we might humble ourselves before our God and ask Him for a safe journey for us and our children, with all our possessions.”— Ezra 8:21 (BSB)