Why?....

[CoolUserName]

A Non-veteran Phalanx unit beat up my Battleship at the Chieftain level, with no city-walls!!!

Dam* this game!!!

 

[CoolUserName]

Oops.
It was an ironclad.

 

[TTG]

lol... FYI the strength of military units is not affected by difficulty level

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<IMG SRC="http://www.civfanatics.com/civ1/units/mbimg/militia.gif" border=0> <IMG SRC="http://www.civfanatics.com/civ1/units/mbimg/phalanx.gif" border=0>
Civilization I Master of masters
Webmaster of Civilization I Fanatics Center

 

[GenghisK]

It was an ironclad.

You've found yourself the answer...
Ironclad (a/d/m) = 4/4/4
Fortified phalanx d = 3.

So although I'm not gifted for mathematics

I think there's ~25% probability to lose. In fact it usually happens.
And FYI, there's another post concerning that "bug" (phalanx winning against battleship or bomber! or nuke losing against normal unit...)

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Genghis K.

 

[TTG]

There's also terrain effects. many terrains have 50% (or more) terrain bonus. On mountain, it's 200%!

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<IMG SRC="http://www.civfanatics.com/civ1/units/mbimg/militia.gif" border=0> <IMG SRC="http://www.civfanatics.com/civ1/units/mbimg/phalanx.gif" border=0>
Civilization I Master of masters
Webmaster of Civilization I Fanatics Center