VOA慢速英语:为什么亚美尼亚和阿塞拜疆在纳戈尔诺-卡拉巴赫战斗？

flare up –v. when violence or disease suddenly becomes worse

breakthrough – n. a sudden and important development

frustrated – adj. getting angry because of not being able to do something or complete something

morale – n. a feeling of happiness or loyalty that a person or group has about a job

drone –n. a kind of small aircraft that flies without a pilot can be used for war

flank –n. a side of a military formation