Military access (abbreviated MA) is a kind of diplomatic agreement between two countries where one country agrees to let the military forces of the other enter its territory freely, and use its provinces to resupply.
Effects of Military Access
There are several effects of military access. Note that military access is not reflexive. The country granted military access and the country granting it do not gain the same effects.
When you've been granted military access by a country:
- You cannot declare war on the country. It may still DoW you, however. You can also enter wars against it in other ways, i.e., if an ally of yours DoWs it and then asks you to join the war. A state of war between two countries does not cancel or negate military access between them.
- You can enter the country's territory when at peace. (Regardless of military access you can always enter it if at war.) If the country has a province occupied by an enemy that is also your enemy, you can siege/retake the province, which will then revert to the control of the owning country (if you're at peace).
- Your fleets may enter its ports, and resupply there. Strangely, they may also capture unfortified ports if you're at war.
- Your land units have increased supply limits while in the country's territory.
Gaining Military Access
There are two ways of getting military access from another country: diplomacy, and force.
Asking for military access from another country is a diplomatic action. It costs a diplomat regardless of the success or failure of the mission, and relations between countries are not affected. Factors influencing success are primarily the military power of the two countries and their relations. Minor factors include the diplomatic ratings of the monarchs and the requesting country's badboy level.
AIs will almost always grant you military access if you've got very high relations (190+), and most AIs except the strongest and most paranoid ones (Timurids, China, Spain) will grant it with 125+ relations. Small countries will grant very powerful countries military access even with relations down to perhaps -25 or so.
Occasionally an AI will ask you for military access. If you grant it, you may revoke it later, costing a point of stability but otherwise without ill effect.
Cancelling and Revoking Military Access
Cancelling and revoking military access are also diplomatic actions costing a diplomat. You can cancel your own access in the other country; you revoke his access with yours. You cannot cancel access if you've got any military unit in the other country's territory. When you cancel or revoke military access with a country, you lose one point of stability. Relations are not affected.
The AI never cancels military access with you once it has granted it, even if the AI is at war with you. Thus, it is often possible to gain military access from a victim country and exploit it in war to reduce the attrition you face. (There are also some other exploits; see the article on military access with enemies.) The AI sometimes will cancel its own military access with you, in the rare event where it has previously asked for it and you have granted it.