Do you really need a plan to wage war successfully?

You'd think so, but I suppose it depends on what "success" means.

There are three parts to it though.

The first is the purpose.

The second is the plan - how to achieve the purpose.

The third is how to deal with the consequences and help repair the damage to cvilians


If a country that starts the war has no clear plan or defined aim then it could claim any outcome to its own advantage to be some sort of "success".

If it has no intention to help the beleagured citizens after the war to repair the damage it has caused, or to contain the consequences, it need not plan for that, either.

If I remember rightly, I once saw a documentary on TV about the Springfield rifled musket. It suggested that a steady supply of rifles made the difference in the American civil war. I don't know whether that's right but it does sound plausible.