Now thats an interesting strategy to use....... Must try it one day.
Edit; did the UK and France declare war on you or just the USSR?
france & uk will declare war on you, USSR it's a bit harder, they have a modifier that forces them to build a certain ratio of troops compared to germany on a border before they can declare war i think, but has time goes on that modifier will come done making it more likely, but Germany can declare war at anytime. So your have plenty of time to drive back from romania, diplo anex austria & 'maybe' the ceczh if you can fine tune the world tension, and be in postion to take france.
The trick to world tension is to do alot with minimal forces, the more troops you build, it increases world tension, if you plop them down, even more so, if you build them as reserves thats cheaper on world tension, the same with techs too, certain tech focused toward arms focused techs will increase world tension, thats the only place you want to be bleeding world tension.
So build your reserves to hold a line againt the french over a due course time, don't plop them down until last min when your forces are coming back from romania it may be cheaper to build planes world tension wise also not sure, but a focus on an army never hurts, although not sure how its calculated, if by IC cost with military units increases world tension, since building factories won't.
I can't remember, but i think it may even be possible to have your cake and eat it, i am sure i also diplo annexed apart fo cezh, and the diplo austria annexation was the final straw for war, or vice versa, so i think it possible to squeeze either austria or half of czechoslovakia in the peace in our time deal. But you need to nail poland before britain can proclaim a guarantee, so you need to get spies in there building world tension, along with romania, and then if you must speed it up by plopping down some divisions, so your beat the brits to poland, it easier then im making it out to be. Theres a rough date that britain will place there guarantee, so until then, you need to force world tension up with poland, so perhaps it may be better to plop down a few full divisions just to grab poland quickly,
also dragging countries into your faction will increase world tensions, so it may be worth inviting them in last minute, or to purposely increase your world tension.
Also so you get your rightful lands in poland with less revolt, check your add war goals, i can't remember, but i think if you add your rightful lands, danzig, then later annexation, i 'think you get the best of both worlds, same with cechs perhaps, unless some war goals just overwrite others. although not sure