New player here - on my 5th or 6th game, but still learning.
Currently, I'm playing Italy. After the Pact of Steel kicked in, I invaded and puppetted both Yugoslavia and Romania*. Later, when the war against Britain and France started, they went to GERMANY'S aid, not mine!
Needless to say, I was somewhat miffed that they didn't come to MY aid, as I was fighting the largest front in France (Germany still hadn't taken Poland, those slackers) and busy with Greece as well.
Do I need to do something to control those troops, or will they always flock to "da boss"?
*which, btw, so upset the balance of powers, that the USA joined the Allies a few months later, along with half of Central America. Patton subsequently invaded/liberated the Netherlands ... in the Spring of 1939. Germany beat Poland, Denmark and the Low Countries, but has done squat against France. Italy has taken the Southern half of France and got all the way to adjacent to Paris before a large BEF force appeared. Now a stack of red colored USA divisions has appeared on the coast of Belgium ... not sure who is controlling them, as Patton's forces were USA Blue. I assume they must be a Expeditionary Force.
You can set allied objectives on a province (bottom of the province screen). This is not a definitive control but might help them go where you want them (also remember to remove once you have conquered it)