The Athenian Navy was the most powerful the world had yet seen. But how powerful is that? Here are some totally spurious comparisons with the most powerful naval force in the world today, the United States Navy.
Let's start with ships of the line.
Themistocles convinced the Athenians to build 200 triremes. By the peak of their empire they probably had close to 300 triremes.
The United States Navy today has 287 commissioned ships according to their own web site.
So the two fleets were almost exactly the same size.
Of course, you might argue the USN has aircraft carriers (11) and nuclear attack submarines (54), which were distinctly lacking in the Athenian fleet. But keep in mind both fleets are the absolute state of the art for their times.
You can be quite sure Themistocles, who clearly belonged to the peace-through-superior-firepower school of international diplomacy, would have had the Athenians building aircraft carriers if only he'd known about them.
In fact a trireme is the equivalent of a modern destroyer. The trireme was a floating battering ram, the first ship in history designed purely to sink other ships, and the fastest thing on the seas. They even had roughly the same crew size: 200 on a trireme versus 280 for a destroyer.
If you think of the Athenian fleet as being like 300 modern destroyers, you're not far wrong. That's a force strong enough to wipe out almost any navy afloat today.
But wait! We're still not making a fair comparison. America is much larger than Athens.
The population of Classical Athens was about 200,000. The population of the United States is slightly more than 300,000,000. Yet they put the same number of ships on the water. Clearly America can afford to invest much less per person and still get a bigger bang. Let's equalize the naval investment per capita.
Adjusting so there are the same number of ships per head of population, the USN is reduced from 287 to one fifth of a destroyer. My money's on the triremes, even if we don't adjust for 2,500 years of technological advance.
Let's try it the other way. If the US made the same per capita naval investment the Athenians did, they would have not 287 ships, but 430,000. No, I didn't type too many zeroes. Even if you count each carrier as worth a thousand destroyers there's still no comparison. Granted it's impossible to compare across such time with any accuracy, but it seems clear there's no nation today making anything like the naval investment Athens did.
The same outrageous ratios apply when you compare the Athenians to their neighbours. The next largest fleet at the time was Corinth, and they had all of 40 triremes. 40 against 300.
The Athenian fleet was huge.