and there would have been more and greater losses had we continued to drift.

问题描述:

and there would have been more and greater losses had we continued to drift.
尤其是那个had在这里充当什么成分?倒装?

这是一个虚拟语气的句子.
had we contintued to drift = if we had contintued to drift
意思是假如我们当时继续飘泊,就会产生更多更大的损失.