I'm beginning to wonder what I'm doing wrong. The naval AI in my games is non-existent to the point of Vanilla level stupidity. In a war against Hiwatha I was burning his little 1 tile cities down to the ground pretty much in sequence and was thoroughly disappointed to find out that he was hiding his rather large Privateer fleet on the other side of his home island absolutely no where near anything of value or looking like it could be fulfilling some strategic purpose.
Needless to say, I sunk them all with the two submarines I had just completed. That part was actually pretty funny, the way the map is set up I simply ended up shooting about half of them from underneath ice where they couldn't reach me! More seriously though is that I'm not seeing the kind of naval production or coordination that I was expecting.
OK, so how does one actually employ sea beggars? So far, I've been using sea beggars to support a land campaign on a long, thin continent. My sea beggars can do some damage to a city, but they get pummeled by return fire from both the city and nearby ranged units.
Are wolfpack tactics the way to go, using several sea beggars in close proximity to take out a city? Are sea beggars better off used in isolated areas (such as islands) far from the main action? Somehow I just don't think I'm doing this right. I'm usually an Immortal player, but I've stepped down to Emperor to learn G&K.
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But how does this Sea Beggar work?
Essentially, yes. To be honest, you don't even really need Frigates. All that matters is the number of points of attack your Sea Beggars/Privateers have on a city. If there's only 1 hex opening out onto the coast then you're not going to be able to rush the city with naval units. 2 or more, however, and you're in business. Simply rush the city with your Sea Beggar/Privateers, you should take somewhere between 1/2 and 2/3 your health in damage on one unit and do a fair number on the city. You might lose a unit in the counter-bombardment phase but that's increasingly unlikely as you start earning promotions. Withdraw back to friendly territory (or if you have Supply just out of range of the city) and heal, then ram two+ more into city. Rinse and repeat.
In my current game I was cycling out a huge fleet (15+ ships more than half of which were captured) between the city I was attacking and my home island some 3 or 4 turns of movement away, and still took the city! Provided you're careful with your promoted units and know when to sacrifice your new/recently captured units it is rather easy, too easy probably, to take cities by sea.
The only issue I've encountered so far is if the city in question is being defended by an artillery, a battleship or similar. In that case, yes, you do need naval bombardment units or a very large number of coastal hex tiles.