crusader-kings-2
I'm trying to play CK2 as a minor count in the service of the King of England, and whenever the King goes to war, I don't seem to be very involved in it – I can basically ignore everything that's going on and just focus on my own holding. If I want to join my liege's wars, I have to raise my own levies and basically follow him around, always one step behind.
Can I give control of my army to my liege, or somehow join my 600 men to his 12000-strong army?
I would go with option one. You say that it leaves you less profit, but that is only partially true. Since you will eventually die and play as your heir, all of that money will drop right back into your pocket. It is possible that your heir will waste some of it, but not a large amount. Most of the money he earns will go back into his properties, and so that gold will end up benefiting you in the long run.
As an additional bonus, if/when your heir wins the war, he will get money and prestige from your non-heir vassal.
Click on the coat of arms of the kingdom of England title. You will see a check box where it says de jure, check that. Then, at the top right of the box, you will see a cost of arms for the de jure liege title of the Kingdom of England, which should be the British Empire. Click on its coat of arms. Then hover over the create button. This will tell you exactly which conditions you need to fulfill to create the title.
This button is also how you create the title and become Emperor. It will be greyed out until you meet all the conditions in the hover-over tooltip.
Here is a three-step illustration of how to find the Empire of Britannia by using the de jure checkbox and liege coats of arms in the Realm view:
Alternatively, you can always use the Find Title button below your world map. Click that, type part of the title you're looking for, and then it will show you matching titles in the dialogue box. Clicking a title will open the same view:
The best way to learn how to use the more obscure parts of the game's interface is by playing the in-game Tutorial. It explains everything and is worth doing once.
Best Answer
As World Engineeer explains, your liege has a right to a certain amount of your levies. Whatever remains, are your personal levies, to use as you please.
However, it is still somewhat possible to give your liege or even just a chosen ally control over your personal levies. Gather round, and I'll tell you how.
Raise the amount of levies you wish to waste away, and march them to an allied force. With your army still selected, this is when you will see this little chain button appear as highlighted in my much too dark screenshot below:
As the highlighted tooltip explains, this means your army will start following the allied army around. This is pretty neat in some cases, such as:
a) Due to severe incompetency on behalf of your commanders (and possibly witchcraft), your once glorious army is reduced to a few hobbling peasants. You are in enemy territory far away from home, and all your ships are eaten by termites. An allied force is nearby, but you don't want to tediously move them manually and risk them being torn to shreds because they moved one day too late. You wisely attach them to the allied force, to keep them protected in larger numbers.
b) You finally did something clever, and managed to persuade your liege to claim some lands for you. Everything is going to plan, but your liege just need that final push to win the war. Your hobbling peasants from before won't do much good on their own though, so as before, you attach them to one of the allied armies. Perhaps they can do some good.
Now, the neat thing about this ordeal, is that it is merely a temporary solution, and you are still the man in control. They just follow those other guys around and take part in their battles. When you get sick of that, or you decide it's time for a tactical retreat, you just unattach your guys and run for the hills.
Bonus info:
Now, there are also many scenarios, where this is unfavourable. Being a loyal servant isn't always your best bet. Some times, it's better if your liege bleeds a little. A hurt, injured and weak liege is much easier to depose. ;)