Now im actually giving a cheap tactic mainly to counter the fact that AI built aircraft. Since some updates, AI have recently been building aircraft and its been doing done serious damage definitely to unprepared guys. I found this annoying as i have lost many high leveled troops(3,4,5,6 promotions). But its basically dependent on intel. This means that as long as you are out of your enemies territory, it is simply fine. Thats why u just need aircraft too. For me, I used 1 aircraft carrier, one jet bomber and one spy. Basically, i used this against australia in true earth start location. U basically send the spy to a coastal city which can be directly invaded by sea. Then, attack the city with the jet bomber. Keep your aircraft carrier away from borders (unless u want to lose it lol). However, make sure the aircraft carrier is in range to attack the city directly. Then, make sure the city is 0 health and then invade it with the aircraft carrier. I have taken almost all of australia’s city’s now.