The Persians placed Samarian army officers in Jerusalem to maintain peace.
feeble Jews: Sanballat's mockery had some truth. The Jews were not wealthy, powerful, or numerous. However, Sanballat did not understand the strength of the God the Jews served.
Can they restore...Will they offer sacrifices?: Sanballat might have mocked the sudden increase in sacrifices at the temple as the Israelites dedicated their work to the Lord.
burnt stones...mounds of rubble: When fire destroyed Jerusalem in 586 BC, it heated the stones, causing some to crack and crumble. The people used these stones to rebuild the walls.