General PurposeEducational
Scope and LevelRange of Command Levels

Military Services Involved

U.S. Navy, Royal Navy, Korean People’s Navy, Civilians

Type of Operations

Surface Engagement

Area of Operations

Off the eastern coast of South Korea near Chumonchin Chan (south of Sokcho)

Number of Sides3
Amount of IntelligenceClosed
Method of EvaluationRigid
Basic Simulation TechniqueComputer

Historical Background (What Really Happened)

AKA Action of 2 July 1950, the Battle of Chumonchin Chan occurred early in the opening days of the Korean War.

Just after six in the morning of 2 July 1950, a UN naval task force consisting of the USS Juneau (CL-119), HMS Jamaica (C44), and HMS Black Swan (L57) encountered four North Korean Navy torpedo boats (#21-24) and two gunboats (Mo-233 & 234). The North Korean vessels were escorting a convoy of 10 transports that had just offloaded their cargo of ammunition at the port of Chumonchin Chan (Roblin, 2019, para. 11).

The four torpedo boats and two gunboats charged at the Allied ships and closed to within 2 miles, but no torpedoes were fired. Based on the later interrogation of a captured North Korean sailor, the Russians had not yet trained the crews on how to fire the torpedoes. In the end, both of the gunboats and torpedo boat #22 were sunk. Torpedo boats #23 and #24 were heavily damaged, with boat #23 running aground on the shore. Torpedo boat #21 turned and ran from the engagement, but its skipper, Kim Kun Ok, later claimed to have sunk the U.S. cruiser, Baltimore (which is false because the Baltimore had been decommissioned and never served in Korea). The North Korean government would later claim a victory (Roblin, 2019, paras. 22-25).

Thus ended the largest naval battle of the Korean War. The North Korean Navy never again challenged UN warships, although the use of small boats for cargo and troop transport continued for the next couple of months. In August, the 10 transports that were escorted by the torpedo boats were found and sunk, as well (Roblin, 2019, para. 26).


A North Korean convoy of at least 10 ammunition transports and 4 MTBs and PC craft has arrived near the port of Chumonchin Chan.

Enemy Forces

In the Chumonchin Chan area, there are known to be North Korean light to medium shore batteries in addition to at least 4 MTBs and PC.

Surface Forces

  • Civilian Junk [35m, armed]
  • Civilian Junk [35m]
  • TK P-4 [Chinese variant of the Soviet Pr. 123K]

Friendly Forces

The Allied flotilla in the area of operations consists of USS Juneau, HMS Black Swan, and HMS Jamaica.

Surface Forces

  • C44 Jamaica
  • F57 Black Swan
  • CL119 Juneau


Patrol the Korean coast near Kangnung and engage any North Korean transports or warships.


  1. Conduct a full sensor sweep of the area
  2. Sink a minimum of 6 transports in the convoy
  3. Sink a minimum 3 of the escorting MTBs and PC craft

After Action Report

*Note: times reported in ZULU Time. For the sake of simplification, I’m only reporting times down to the minute, although the game-generated message log is more specific and records down to seconds.

The scenario begins at 2115 (0615 local). Wind & sea state of 3 with no rain and light clouds at 20-23k feet. We have four hours to complete our objectives.

HMS Jamaica fires opening shots 2115-2125

I immediately have all three Allied vessels turn on their radars to begin identifying surface contacts. I order USS Juneau to continue northwest at flank speed to join up with the Royal Naval ships. I have HMS Black Swan move towards the shore at flank speed to get targets within range of her weapons, and I have HMS Jamaica increase speed to ahead full.

At 2115, I immediately have Jamaica begin firing on three PT boats. At 2116, Jamaica transmits a radio message, “Enemy cargo vessels spotted. They’re attempting to scatter. Tally ho!” By 2117, the three targeted PT boats have been destroyed. At the same time, I order Jamaica to target another PT boat and change her Weapons Release Authorization (WRA) to hold fire on using her torpedoes. Around 2119, I order Jamaica to begin turning to port and doubling back on her course. By 2120, the Jamaica has sunk a further 2 PT boats and 1 armed civilian junk. By 2121, Jamaica positively IDs 2x armed junks and opens fire. They’re both sunk by 2122.

HMS Black Swan opens fire 2125-2134

At 2125, a transport junk is identified as hostile and is sunk by gunfire from the Black Swan at 2127. By 2130, four additional transports have been sunk by Jamaica and Black Swan. Around the same time, Jamaica begins engaging a 76mm shore battery and, along with Black Swan, engages additional transports and armed junks.

Pursuit south 2134-2140

By 2134, the three remaining vessels are fleeing southeast. At 2135, Jamaica has destroyed one 76mm battery of six guns and proceeded to fire on another 76mm battery which is destroyed by 2139. She quickly shifts fire to another battery.

USS Juneau joins the fight 2140-2145

Around 2140, USS Juneau joins the engagement and fires on the three vessels fleeing south. Black Swan fires on them in pursuit from the north. By 2143, the remaining three junks are sinking. Simultaneously, Juneau opens fire on a radar site which is destroyed by 2145.

Mopping up 2145-0048

The remaining shore batteries are destroyed by Jamaica and Black Swan by 2155. Jamaica, on a looser Rules of Engagement (ROE) begins opening fire on the town of Kangnung before I order them to cease fire. I then order Jamaica to move to the north-northeast, Black Swan to the east, and Juneau to the south-southeast for a surface search of the surrounding area. At 2226, Jamaica makes radar contact with 2 surface contacts. She identifies them as neutral fishing boats by 2341 after closing to visual range. At the same time, Juneau detects a surface contact. At 2358, Black Swan detects a surface contact. At 0030, Juneau classifies her contact as civilian. At 0048 Juneau detects another surface contact. The scenario ends before a positive identification could take place.


United NationsNorth KoreaCivilian
5x TK P-4 [Pr. 123K]
5x Civilian Junk [35m, Armed]
10x Civilian Junk [35m]
30x 76mm/30 M1902 Towed Gun, Dug-in
2x Radar (Generic Surface Search Radar)
694x 102mm/45 Mk16 Twin HE Burst [2 rnds]
360x 152mm/50 Mk23 Triple CPBC Salvo [3 rnds]
145x 152mm/50 Mk23 Triple HE Salvo [3 rnds]
278x 40mm/60 Twin Bofors Burst [4 rnds]
27x 40mm/70 Mk7 Single Bofors Burst [4 rnds]
300x 127mm/38 Twin HE-PD Burst [HiCap, 2 rnds]


*Note: Although this scenario is based on a historical event, it is not meant to be an accurate recreation. The point is to examine our own play of the scenario.

Interestingly, historically the Allied ships engaged four PT boats and two gunboats, but the scenario depicts five of each.

This is a very straightforward scenario that’s good for beginners because it’s a purely surface action naval battle. There are not many variables to take into account. Given the small size and tactical nature of the scenario, I’m focusing the evaluation on the educational (decision-making) aspects of the gameplay. I could break down the statistics even more and start calculating average hit rates for each weapon and the number of targets they destroyed, but I don’t see the point since the more advanced realism settings for this scenario, such as detailed gunfire control, are disabled which removes certain tactical factors from influencing the hit probabilities for weapons. Furthermore, the UN naval forces have overwhelming superiority in firepower and range.

The HMS Jamaica and HMS Black Swan start off in an advantageous position to cross the T with the North Korean PT boats. The USS Juneau is further south and needs to rush north at flank speed to join the engagement. One thing to note throughout the battle is that the Jamaica and Black Swan do the majority of the fighting. The Juneau is so far south that it seems almost superfluous to the scenario. By the time it joins the others, most of the enemy vessels have already been sunk.

At the start of the action, my initial assumption is that any unknown naval vessel close to the shore is hostile (then again, I’ve played this scenario before and have the benefit of hindsight…HeHe). Even at that, PT boats can be very dangerous in the littorals because they can use their high speed to close the distance quickly and launch their torpedoes which can do devastating damage to a ship. So, it tactically makes sense to engage them quickly. I restricted Jamaica from firing torpedoes because, for whatever reason, any torpedo fired by UN forces deducts points from your final score. Maybe the reasoning for that is because if the North Korean PT boats get close enough for you to use your own torpedoes, then that means they’re also in range to use their torpedoes. It’s a tactically bad decision, so don’t let it happen! But, I’m speculating.

I had Jamaica turn to port and reverse course because of the potential risk of enemy torpedoes. Post-scenario expenditures show that no torpedoes were fired from any PT boats, but it’s better safe than sorry. The PT boats were the first enemy vessels destroyed, which left the armed junks and transports. By then the HMS Black Swan was in range and contributed her firepower. The Black Swan was in a better position to pursue the three transports fleeing south, but the approaching Juneau also managed to cut off their escape and the two Allied vessels caught them in a cross-fire.

Though the scenario doesn’t specify the conditions for the sensor sweep, I sent the three ships in different directions to locate any potential shipping traffic that was away from the coast. In the end, several more vessels were detected by surface search radar but were not identified before the end of the scenario.

Overall, this is probably one of the easiest scenarios to achieve a perfect score on. We accomplished all of the objectives and achieved a score of 3000, resulting in a triumph.

Lesson(s) Learned

Given the simple setup and easy difficulty of this scenario, the biggest lesson is the reinforcement and application of basic unit movement and attacking procedures, as done in the game’s tutorials.


Short of actually losing the battle or getting ships sunk, what sort of alternatives, of undoubtedly many, could we postulate?

  • I could have let Jamaica and Black Swan engage the KPN vessels and shore batteries and instead sent the Juneau to conduct a sensor sweep of the surrounding waters instead of rushing north.
  • I could have formed the Jamaica and Black Swan into a different formation, such as line ahead, for the engagement.
  • I could have ordered Jamaica to focus on a specific type of target such as the PT boats or shore batteries using her longer-ranged weapons. Meanwhile, Black Swan could have specifically engaged the fleeing transports and Juneau could have cut off any escape route to the south.


Roblin, S. (2019, September 7). How British and American Cruisers Shut Down the North Korean Navy in a 10-Minute Battle in 1950. Retrieved from