含蓄条件句

Five minutes earlier, and wecould have caught the last train.

各位老师，我想问问five minutes earlier这里是什么省略使用方法？假如结构是祈使句，and＋句子，为何前面没Arrive/Be？

谢谢老师！

祈使句,+and +陈述句表示的条件句，可以把祈使句进一步简化为一个名词词组，就是你提问的如此的句子。它等于：

If we had arrived five minutes earlier, wecould have caught the last train.

又如，老板对一个职员说：One moremistake, and you will be fired. = If you make one more mistake, you will befired.