Code:
decision_trigger = {
event = 2003009
OR = {
owned = { province = 195 data = GER }
AND = {
control = { province = 195 data = GER }
war = { country = GER country = AUS }
}
AND = {
OR = {
alliance = { country = GER country = AUS }
relation = { which = AUS value = 200 }
}
event = 2003008
}
}
}
This is the event. This boils down to:
Austria MUST be couped (via event; 2003009 is informing GER of 2003008, the coup in Austria).
And then either:
1. Germany owns Vienna (i.e. Austria has already been annexed)
2. Germany controls Vienna and is at war with Austria (i.e. Germany went to war to annex Austria)
3. Germany is allied with Vienna or has 200 relations (i.e. Germany allied Austria for annexation ...the sort of 'historical' option)
(...and the coup event fired (2003008) ...which is redundant, since it triggers the event (2003009), which all three of these require anyway. The only purpose 2003009 serves is switching the Germany AI for the Anschluss)
The most difficult part is getting the coup event to go off in the first place. And for that you need the Pact of Steel with Italy, which causes them to end their guarantee of Austria. Italy has a chance of signing the pact early, but after the historical date they have a 90% chance. This means if they do sign it on the historical date you may still need to wait up to 30 days for Austria to be couped (and it only has a 55% chance of occuring each time until 1939, so you may be waiting longer).
[edit]Maybe the confusion is why you would bother using the decision if you've already annexed Austria? Because that is easy to answer: you get bonus manpower, -10% dissent and all sorts of other fancy bonuses aside from just the IC and latent manpower of the provinces.