A pesar de todo ello, descuidos y errores durante la guerra hicieron que fueran prácticamente aniquilados por los barcos de la Armada de los Estados Unidos. Errores de diseño, derivados de un desplazamiento limitado y la acumulación de armamento, causaron que ciertos barcos fueran inestables y demasiado pesados. Si bien la concentración de su armamento antiaéreo en una única fuerza era tan eficaz como revolucionaria, sus artilleros no estaban protegidos de los contraataques debido a la falta de radar y la mala configuración y diseño de los cañones antiaéreos. El ataque sorpresa a Pearl Harbor efectuado en Hawaii en el 7 de diciembre de 1941 fue una victoria táctica pero a la vez un error, llevando a la guerra a una nación que, pese a no estar preparada inicialmente para la misma, sí tenía una capacidad industrial inimaginable. Además, ninguna de las instalaciones de Pearl Harbor fue atacada —astilleros navales, depósitos de combustible, infraestructura de logística—, permitiendo que Estados Unidos se recuperara rápidamente y contraatacase a modo de venganza desde su principal base en el Pacífico. En contraste, Japón no tenía esa capacidad para recuperarse ya que dependía de las importaciones —hecho el cual motivaba las ambiciones de expansión de Japón— y sus líneas marítimas no estaban preparadas dada la escasa inversión realizada en sistemas de guerra antisubmarina y antiaérea, lo cuál permitió a la Armada de los Estados Unidos someter a Japón lentamente.
Los barcos japoneses tienden a tener grandes variaciones en su diseño; cada clase tiene un modo distinto de manejo respecto a su tier anterior, resultado de los experimentos constantes de la IJN e influenciado por diferentes diseños y doctrinas. Cuentan con torpedos superiores, cañones de largo alcance y precisos con gran capacidad de daño, además de una excelente maniobrabilidad y ocultación; sin embargo, sufren en su supervivencia y armamento antiaéreo. Su estilo de juego es muy similar a la doctrina de la “batalla decisiva” que dominó las tácticas de la IJN: atacar rápido y fuerte, con precisión en los objetivos de importancia y/o oportunidad, pero sufriendo dolorosamente, a cambio, con cada golpe realizado.
Japanese destroyers rely on remaining unspotted and depend heavily on making good use of their torpedoes; the tech tree splits at Tier V after Isokaze, with one line focusing on torpedoes and the other on gunnery, the latter currently ending at Tier VIII.
The line focusing on torpedoes have weak, slow-turning guns that are generally not worth firing unless they happen to be pointing in the enemy's direction. Even then, it is frequently better to hold fire to maintain concealment. Concealment issues are exacerbated with the Smoke Generators on Japanese destroyers having fewer charges and shorter durations, giving captains less flexibility to get out of sticky situations. Their torpedoes are unmatched at every tier, having the highest damage and longest ranges of any vessel that can equip torpedoes. This allows them to snipe enemy warships while well out of visual range. Starting with Yūgumo at Tier IX, their guns begin to be more effective and captains get to choose from three types of torpedoes: high-speed (up to an incredible 76 knots) but shorter range, very long range but low speed ("low" being something of a misnomer, given that they still move at more than 60 knots), and an in-between option that has average speed and range. This allows for variable play styles and keeps opponents guessing. Combined with the Torpedo Acceleration skill the short-range torpedoes can be particularly vicious; it is almost impossible for enemy captains to dodge torpedoes streaking in at a whopping 81 knots.
The gunnery-focused line does not mean that they become pseudo-American destroyers, but many of the problems that plague the torpedo-focused destroyers are addressed to a certain degree, increasing their all-round capabilities while still keeping the distinctive characteristics of Japanese destroyers. However, all these improvements are "implemented" in an arduously gradual process — captains will only start seeing real differences once they reach Shiratsuyu and Akizuki at Tiers VII and VIII, respectively. Their turret-turning speeds are improved, their guns fire faster and further (shell damage and velocities are largely the same) and they have better anti-aircraft suites. Amazingly, their concealment values are better than that of the torpedo-focused line, allowing them to fire their main battery guns undetected like American destroyers, and both lines have access to the same models of torpedoes. What's more, the gunnery-focused line gets a better version of the Torpedo Reload Booster consumable! Unfortunately, they (rightfully so) get fewer torpedo launchers with longer default reload times, and their mobility is among the worst for destroyers, with inferior speed, maneuverability and underwhelming acceleration.
Japanese cruisers tend to have fewer guns housed in slow-turning turrets, coupled with excellent maneuverability and concealment values. Virtually all Japanese cruisers are equipped with a complement of torpedoes that are on par with their destroyer cousins. At the higher tiers, their torpedo tubes are often located aft of the vessel. Do not be fooled if a Japanese cruiser starts turning away mid-fight; they may have very likely just launched a spread of torpedoes in your direction. From Tier V's Furutaka onwards, they are equipped with accurate, powerful guns that, while lacking in rate of fire, have reasonable shell arcs and velocity and are able to reliably penetrate or set their enemies on fire - their high explosive shells have a highest chances amongst all cruisers in World of Warships to set targets on fire. Their anti-aircraft suites are sufficient for self-defense, but captains will be hard-pressed to protect their teammates. The Tier X Zao is considered the very pinnacle of what the Japanese had expected of their cruisers: difficult to detect, she strikes first and hard. She is capable of giving enemy ships a nasty surprise when they are at close range and is a highly effective surface combatant in all situations.
Japanese battleships were somewhat restricted by the Washington Naval Treaty, forcing them to resort to unusual — but often innovative — designs in outfitting their battleships. This resulted in battleships that have widely varying characteristics: the ponderous and slow Kawachi; the fast and agile Kongo; and the well-balanced Nagato; culminating in the crown of their battleship tree, the formidable Yamato. Japanese battleships often have the highest caliber guns with the longest ranges of their tier, which they can extend even further still with Spotting Aircraft, allowing them to rain destruction upon their enemies with impunity. Many of them have good speeds and agility that belies their size and class, but their armor protection frequently lags behind their counterparts of other nations - it tends to be more evenly spread out around the entire ship, so while their citadels may not be as well-protected, they have few obvious weak spots. Like their cruiser cousins, their anti-aircraft firepower is sufficient for self-defense, but you will be wanting cruiser support to ward off more concentrated aerial assaults.