Thanks for posting that bit from the Commentary/ from St. Augustine. Is that a book you own? Very interesting. I did not know that Luther counseled NOT fighting the Turks — that must have to do with Lepanto?? I had read only that the Protestants were involved in the Reformation and so not available, but not that they chose NOT to fight.
"To fight against the Turk is the same as resisting God, who visits our sin upon us with this rod of his anger."
Source: http://www.puritanboard.com/f24/martin-luther-war-against-turk-40430/