What might be the risks of refusing to help an ally?

[Jones]

I'm doing my history homework i don't get it. I'm talking about an ally in war. Our class is discussing about wars in Europe right now.

[aero]

Well, it depends on the ally: how important is their role in your economic community. For if you take on an ally that is closely meshed with your economic system then you risk setting the whole economic market out of balance if such close partners quarrel. However, if your alliance is that of one in which you are united against a common enemy then turning away from the alliance puts you at risk. This is due to the fact that one usually enters into an alliance to fight against a more powerful adversary and that if you break that alliance down then both you and your ally's strength is hurt and leaves you vulnerable to an enemy strike or move against you. This is kinda a general answer but...yeah...

[Hawke]

Think about it this way - what would happen if you promised a friend that you'd do something and then refused to?  

Thats a rough approximation of one ally refusing to meet his obligations to another.  Acctual consequences will vary depending on the situtation.  Since I'm assuming you're talking about WWI I'll use it as an example.

If England refused to declare war against Germany when France was attacked the consequences would be dire if France survived the war.  The least that France would do would be to declare a trade embargo against England.  This means that France would not trade goods or services to England, nor allow other nations to ship goods thru France or French territory to England.  This would have seriously hurt the English economy (think Great Depression).  At the extreme France would declare war on England. So either way you cut it, England would lose if they didn't support their ally.

Taken further, England's reputation would be tarnished.  Nations would not enter into agreements with England or trust the England.  This would make it difficult for England to run its economy and stay a strong, independent country.  There can be no worse action than pledging support and then not delivering.  A country that does not fulfill it's treaty obligations becomes an outcast.