Prologue: The Battle of Pacocha

On 29 May 1877 an indecisive naval battle was fought off the coast of Peru. 

The Peruvian armoured monitor Huascar had been seized by rebels in an attempted military coup and was harassing merchant ships. A Royal Navy squadron consisting of the unarmoured frigate HMS Shah and corvette HMS Amethyst, under the command of Rear Admiral Algernon de Horsey, was sent to deal with her. The Peruvian ship was unable to hit the British vessels, whilst the British shells were unable to damage the Peruvian vessel. After dark the monitor slipped away, and the battle was over.

The significance of this battle for this campaign is that in January 1879 HMS Shah was on her way home to England when she heard about the disaster of Isandhlwana. Captain Bradshaw, on his own initiative, diverted the ship to South Africa to land a Naval Brigade, picking up the garrison of peaceful St Helena on the way. Shah would land 378 of her own bluejackets, plus two 9 pounder guns, four rocket tubes and two Gattling guns. In addition, she brought from St Helena 161 soldiers and two 7 pounder guns. In this alternative timeline, with a global conflict raging, these are going to be the only reinforcements that will arrive.

If HMS Shah ends up on the bottom of the Pacific in 1877, Lord Chelmsford will be down a battalion of foot and a battery of guns. With that knowledge, de Horsey would not press this battle too hard. So, what you need to fight this battle is an admiral who knows nothing of this. Instead, they need to believe that the honour of the Senior Service is at stake, and that they don't want to be the first Royal Navy Admiral to lose a battle since Admiral Boyne. 

RULES

I don't like paying for rules if I don't have to, especially if I may only ever fight one battle with them, so I use Dark Days of Admiralty which are available free from Guildford Wargames Club.

http://guildford-wargames.org.uk/info/?page_id=60

The one modification I use is to say that guns which only have a Pen. S.V. of 1 do no damage if they fail to penetrate armour. As most of Shah's armament consists of these weapons, this is important. I've rated the armour class of the Huascar higher than the rules suggest. This is based on the actual battle, where Birkenhead's iron did a very good job of keeping out the Woolwich shells. 

The rules also contain no provision for using torpedoes. The one thing that puts the Battle of Pacocha in the history books is that it was first time a Whitehead torpedo was fired in anger. Seeing as the torpedo was actually slower than the Huascar this was always going to be a long shot, and it was not a surprise that it missed. Torpedoes were the future, but not fired from ships of the line. The only battleship ever to hit another with a torpedo was HMS Rodney, who hit the Bismarck. However, Admiral de Horsey was not to know this, so perhaps we should let him fire his torpedoes, but make him have to roll some unlikely combination of dice to actually have them hit anything. 

HUASCAR

The Peruvian ship is a turret ironclad launched, rather ironically, in Birkenhead in 1865, and armed with 10 inch muzzle loading guns made, ironically again, in Newcastle. 

On 6 May 1877 she was seized by Colonel Lorranaga as part of an attempted military coup whilst her captain was ashore. He persuaded some of the officers, and all of the crew to join, him and put one German Astete in charge. No other Peruvian naval vessels were in a condition to stop him. She patrolled the Peruvian coast attacking government ships. In the process, some neutral shipping was attacked, including British merchant vessels. This brought the wrath of the British Empire down on the ship. 

The stats for Dark Days of Admiralty are:

Type: Older Battleship

Flotation value: 5

Movement boxes: 6

Armour Class: BC

Armament: 

2 x 10 inch muzzle loader in Coles turret. Accuracy B, Power 3, Pen S.V. 2

2 x 4.7 inch muzzle loading guns. Accuracy E, Power 5, Pen S.V. 1

HMS SHAH

HMS Shah was launched in Portsmouth in 1873. She was made of metal, but was unarmoured. Although classed as a frigate, she was really a cruiser. Her armament was two 9 inch, sixteen 7 inch and eight 5 inch rifled muzzle loading guns, and four torpedo tubes. After being decommissioned her masts were used in HMS Victory, where they remain today.

Her stats for Dark Days of Admiralty are:

Type: Unarmoured

Flotation value: 13

Movement boxes: 8

Armour Class: UP

Armament: (each broadside)

1 x 9 inch muzzle loaders. Accuracy C, Power 3, Pen S.V. 2

8 x 7 inch muzzle loaders. Accuracy D, Power 4, Pen S.V. 1

4 x 5 inch breech loaders. Accuracy E, Power 5, Pen S.V. 1

BATTLE

The battle begins with the Huascar fleeing and the British ships pursuing. HMS Amethyst is purely an observer in the battle, as her guns are useless against Huascar. At some point Shah will either come alongside Huascar, or one vessel will turn to bring its guns to bear, and the battle begins.

I fought this battle with a suitably aggressive Admiral de Horsey in HMS Shah. A lucky hit on Huascar's bridge allowed her to do some serious damage to the Peruvian vessel from close range. However, just before Huascar sank, a replacement captain regained control and hit Shah with a broadside. The Peruvian vessel went down, but by the time she did so HMS Shah has suffered 75% damage and had a serious fire raging. The crew got it under control before she followed the Huascar to the bottom, but it had been a damn close-run thing. 

There is an excellent account of the real battle here:

https://web.archive.org/web/20040803142718/http://members.lycos.co.uk/Juan39/BATTLE_OF_PACOCHA.html