I am playing as the US. I am allied with Japan, SK, Siam, India, UK, and Isreal. I have an official alliance and a two sided defensive pact with all of them. While there are a ton of wars going on the ones that are important are India and china, Russia and China, SK and china, India and NK, SK and NK, Russia and NK. I have a transport treaty with Russia and have been doing a little bit of trade with them. SK and Japan are allied with Russia. I have a 100 CB against russia (they have been building a ton of military structures (over 80 aircraft fabrication facilities alone)), but only 27 percent to most of the other countries. Most of this is happening in the years 2021-2023. I play on military and diplomaticly at Very Hard, until I am about to declare war then I will lower it to very easy then bring it back up after.
I did not want to jump in and attack NK right away becouse I was afraid that Canada would come after me and I wanted to work a little on my budget before i went crazy with war. However I was giving NK and India supplies for thier war efforts. Even using my supply air units to keep thier front lines in supply up in china's western boarders. I moved ground troops into SK and moved them to the front lines hoping to discourage NK from attacking. (I would get hit from NK and get the option to ignore or declare war). After anouther year I finaly had the longer range arty that I would need for a war with NK. And had the reserve troops to defend an attack from canada or Mexico. I then positioned the rest of my troops in SK and prepared for war with NK.
So in the defense of my ally I declare war on NK.(and by this time japan and Siam are at war with China, and india is at war with NK) Everybody hates me allot for doing this. Well crap. ok so I reload to just before declaring war. Hmm maybe if I move my units to the frontlines again and they get hit by NK. and I use that declare war option. I did that but it had the same effects as just declaring war. Ok so the only other way I know to declare war without everyone hating me is a border incursion. And thats what I do, allot of people hate me but not as bad as just declaring war. I even lost people support with SK. Hell I was coming to save thier ass and they dont like me for it.
Now I did this war with NK 5 or so times. reloading to just before to try out a few different stratagies. There are a few key things I want to point out here. On one attempt I left my units to passive hoping SK would follow up behind me conquring the land so I could keep my units in supply. Yea this did not happen..... On anouther attempt I went active and conqured the land so I could keep my units in supply However once I got controlled all the SK bordering land and moved half way up into NK, SK was not assisting me in the battle against NK, Also SK's relations droped even further becouse of this.... So then on the final go at it. I moved my forces up the north eastern part of NK. Leaving a gateway for SK to more threw NK on the south western side of NK. However I was using my arty and my air units to keep that portion of NK clear so SK could move its troops forward. Now SK never moved its troops into that portion of NK even while I was well into china's and russia's territory.
Which brings me to my next point. Once I get a boarder with russia they declare war on me. I mean I am at war with the people they are at war with, we have transportation and supply treaties. I am not at war with anyone they like. So they should be happy that I am defeating thier enemies for them. But instead they declare war on me. I wrote it off as them being upset that I was taking the land that they wanted to attack and so they attacked me. So at this point in time I am like fine screw it instead of being the helpful police country that I am, I am just going to have to conqure the world and regulate thier freedoms threw total control.
So my whole point is its stupid that you cannot assit your mutual defense ally without the world coming down on you. However I do have a solution to this. When you have a mutual defense treaty with a country and an alliance. When your units are on your allies territory and they are on the frontlines. If they get hit by the attacking country or are forced to move from thier location from thier location, you already get a report that says you have been attacked by a neutral country with the option to ignore or declare war. But the new option would be:
Ignore (loose relations with your ally).
Declare war (You would not recieve as much CB as normaly declaring war would cause)
Propose peace (increase your CB on that nation. Increase your relations with the UN and allies, slightly increase the two waring nations relations(so it has a higher liklyhood of success)).
Ask for assistance (the allies of the your ally with move units there too)(which will evenualy cause a joint operation against the enemy)