After the defeat, the country secretly began planning a revenge movement to regain the lost border provinces.

revenge 是名词，意思是"复仇、报复"，指对伤害或失败进行回击的行为。这个词来自古法语，强调对所受伤害的报复性回应。revenge movement 指"复仇运动"，即为了报复之前的失败而采取的有组织行动。