The Imperial Russian monitor Novgorod, sole ship of her class, was
in service from 1874 until 1903; Popov, similarly, from 1876 to
1903.
Yes, of course this post arose from recent discussion of the term
"monitor". These ships were monitors in the American sense, a design
that pushes towards the "guns" point of the guns-speed-armour tradeoff
while not completely ignoring the other two.
The distinctive thing about these ships are their circular deck plans.
Why, you might ask, did anyone think this was a good idea? Well, the
convention at the time was to make ships longer and thinner (for
higher speed for the same power); but the closer an object gets to a
circular plan, the more thickness per area you get from a given weight
of armour, the heavier guns you can mount, and in theory the shallower
you can make the draught. The Scottish shipbuilder John Elder proposed
widening the beam in an article in 1868.
Meanwhile, at the end of the Crimean War in 1856 Russia was banned
from keeping a battle fleet in the Black Sea, but wanted to defend the
Kerch Strait (connecting the Black Sea and the Sea of Azov) and the
mouth of the Dneiper (navigable all the way to Dorogobuzh). Rear
Admiral Andrei Alexandrovich Popov was looking for shallow-draft
vessels and took this idea further, to a design that would be fully
circular, and with a flat bottom.
Novgorod was intended to be the first ship of ten, with two 11" guns
and just over 100 feet in diameter. Popov (originally Kiev but
renamed by Tsar Alexander II after the designer) was intended to the
second of the class, but was enlarged during construction, ending up
117 feet wide and 126 long, with two 12" guns. Each ship had a single
turret in the centre and apex of the deck, with an unarmoured
superstructure forward, smokestacks to either side, and a bridge aft.
They were stable gun platforms. Novgorod at least was too slow to
make way reliably upstream against the Dneiper currents on an ebb
tide, and so hungry for coal as to restrict operational range to
400-odd miles; in anything more than a flat calm they both rolled and
pitched enough to prevent loading or firing of the guns, sometimes to
the extent of the propellers coming out of the water.
But contemporary accounts of their steering ability are wildly
divergent, and nobody who could be regarded now as a trusted observer
ever seems to have written about the things. Some said that even
running half the engines in reverse couldn't turn them in less than
several minutes and they spun uncontrollably when the guns were fired
(these seem like two incompatible characteristics), others that they
could quickly rotate in their own length as needed. Some writers were
foreigners wanting people to laugh at the Russian navy; others were
Russians talking up their own force. They hadn't yet evolved the level
of sophistication of outsiders talking up the enemy to get more money
for their own fleet; that had to wait for the 20th century.
These ships certainly weren't useless. For lurking in calm weather
around river mouths and straits, where any ship that could get to them
would be too light to fight them, they were at least a plausible
threat, and the fact that they were kept in service for nearly 40
years supports this too. I can see no evidence that they ever saw
action, but in some respects that's the best sort of ship, that the
enemy doesn't believe it can beat and so never attacks.