The entire connection with surrender on a battlefield does not correlate well with the salvation concept. You surrendered, you became slave, captive! Ho, ho this is a watered down meaning of pisteou. Same illustration but I would like to make a difference for to understand the concept of pisteiou in salvation. Just hold the forth, Jesus is coming to save you, just believe and see the salvation of the Lord! This emphasize rather a rescue, deliverance from the enemies. This means freedom, safety, and victory!