Many families had to abandon their homes and flee to neighboring countries when the war broke out.

abandon 是动词，意思是"放弃、抛弃"，指因不得已而完全放弃某物或某地。这个词来自古法语，原意是"放弃控制权"，在现代英语中常用来表示被迫放弃或遗弃。