When your manufacturing and shipping capital is on a small island, reliant on a sizeable fleet of galleys to import supplies and export the resulting goods, it miiiiight be a good idea to build some more combat-focused ships for defense.
Particularly before declaring independence from Europe.
I have loads of guns and manpower... on the continent. The expeditionary force knew better. The fleet quickly bombarded my capital's walls into nothing, then overwhelmed the green defenders with massive waves of elite troops. Then they pushed a few cities into the continent... But between terrain bonuses, patriotism bonuses, and just having a veritable swarm of green infantry, I pushed them back into the sea.
At which point they apparently went "k" and camped out on my island, their warships hunting down my galleys and blockading my ports. Their remaining land force is actually pretty tiny, I just can't get my army to it! It's like if the British captured Cuba and considered that a win. Which is the kicker- it's a fairly generous timer, but I need to wipe out the European forces or "lose".
I even managed to scrape together, via upgraded warehouses, enough gold to equip a ship-of-the-line. Supposedly the best defensive ship in the game- oh, it died instantly. Balls. You know what, I'm declaring this a "draw".
Civilization 4: Colonization