Who are the "idols of our hearts" that Twain refers to in the war prayer

Twian is refering to the country's soldiers.

The War Prayer was written by Twain in opposition to the Philippine-America War. He opposes the insurrection brought about by differences in religious beliefs and thus is shown in this short story. His commentary is how can people go to war and pray for God's grace at the same time? He finds it ironic and ridiculous. The reference to the "Idols of our hearts" goes to the soldiers and believers of the war. Twain ridicules them with this statement. This work might have been seen as sacrilegious at that time and was published posthumously for Twain believes that "only the dead can tell the truth in this world".