For over four decades, the Soviet Union built thousands of small ships armed with anti-ship missiles or torpedoes. Every communist country had at least dozens of these small boats, that were, in theory, capable of devastating fleets of larger ships. Never happened.
Most of those Soviet era FACs (Fast Attack Craft) have disappeared. This is because that, while the Soviet designs looked impressive, they didn't work as they were supposed to. Most FACs were too small (under 200 feet in length and 200 tons displacement) to be effective. If there were any waves about, and the FACs were moving at high speed, the violent bouncing off made by the small ship pounding through the sea made it impossible to keep the radars and missiles operational. For decades, the FAC admirals explained this away by pointing out that PT boats were only successful when they approached their targets slowly, in calm seas, at night. That's true. But as a practical matter, FACs rarely encountered those optimal conditions.
These deficiencies were quietly noted by Soviet ship designers, and towards the end of the Cold War, new classes of larger (closer to 300 feet long and 1,000 tons displacement) missile boats. These became known as corvettes. In another one of those historical ironies, the modern corvette is the same size and displacement as the original destroyers that appeared about a century ago. Actually, these ships were originally called "torpedo boat destroyers," as their main task was to use their guns to sink smaller (about a hundred feet long and under 50 tons displacement) MTBs (Motor Torpedo Boats) trying to get close enough to destroy a battleship or destroyer with torpedoes. They succeeded a few times. But during World War II, MTBs grew a bit larger, were armed with machine-guns and small cannon (in addition to their two or four torpedoes) and made themselves useful as patrol boats. Actually, the torpedoes were often taken off and kept in a less hostile environment ashore. Torpedoes were the first guided missile, and required a lot of maintenance to keep them operational. Bouncing around on an MTB was not the best way to keep a torpedo in working order.
When World War II came along, MTBs were still around, a little larger and heavier, and with more reliable engines and torpedoes. The "M" in MTB indicated that these craft used diesel or gasoline motors rather than steam engines (as all larger ships did.) The motors allowed the MTBs to get up more speed more quickly, but limited their range because of high fuel consumption. The MTBs handled badly at high speeds in rough seas, and were basically coastal craft. But in wartime, there were many situations where the "front lines" were often at sea, in coastal areas or regions containing lots of islands.. In the Pacific and Mediterranean, PT (for Patrol Torpedo) boats spent the vast majority of their time patrolling. Their machine-guns (up to 20mm) were often used against enemy PT or supply boats, as well as enemy aircraft.
Despite the success of PT boats for patrol work, the U.S. Navy got rid of them by 1946. The USN was leaving coastal patrol to the Coast Guard (at home), and army (overseas) and heading off for the high seas. The Russians, and other communist, however, were strict about who entered, or left, their territory. So PT boats (many without the torpedoes) remained popular and numerous. When Russia introduced the first anti-ship missiles in the late 1950s, no one really paid much attention. But when one of these missiles (a SS-N-2 Styx) sunk an Israeli destroyer in 1967, the world noticed. The Egyptians, using a 75 ton patrol boat armed with two 2.3 ton Styx missiles had taken out a much larger ship. It happened again four years later during an Indo-Pakistan war. But after that, nothing (or not a whole lot.) In the 1973 Arab-Israeli war, Egyptian and Syrian boats fired 52 missiles without hitting anything. The Israelis were prepared with electronic devices that jammed the guidance systems.
But Russia went on selling those little boats, and the big missiles to go with them, for another twenty years. Slowly, however, most admirals figured out that these little boats with their big missiles were a poor investment. When you bought the system, most of what you were paying for were the missiles and fire control system needed to give it half a chance to hit something. Then you ended up using the FACs as patrol boats. This beat up the missiles big time and you couldn't afford to keep repairing the damn things. So after a few years you had FAC's with broken missiles still performing pretty well as patrol boats.
To the Russians credit, they figured all this out as well and began producing larger FACs, and selling the smaller ones without the missiles (for use as patrol boats). But Western builders were able to sell larger FACs with smaller and more reliable anti-ship missiles (like Harpoon and Exocet.) When the Cold War ended, so did Russia's captive market of communist nations. Within a few years, the old Soviet style FACs were disappearing fast. China still made copies of the old Soviet FACs, but few nations were dumb enough to buy and use them. North Korea was one of the few users. That's about the only good news to come out of North Korea in a long time. Anyone using FACs against a modern navy is mainly providing targets, not a credible threat.