military reserve
units, personnel, and resources not initially committed to battle and available to a commander
en-US/ˈmɪləˌtɛɹi ɹiˈzɝv/
en-GB/ˈmɪlɪtəɹɪ ɹɪˈzɜːv/
units, personnel, and resources not initially committed to battle and available to a commander