During World War II (WWII), there were many differences between the American (United States Navy—USN) and Japanese (Imperial Japanese Navy—IJN) aircraft carriers. This was largely to do with cultural and technological changes combined with different battle strategies. For example, the IJN chose to focus largely on offensive tactics, believing that defense was of low priority. Because of this, their carriers were not built to be self-sustainable in taking on damage, leading to the carriers not being able to easily bounce back from significant damage. This made the IJN aircraft carriers easy targets for USN ships, because—although they were incredibly on the offensive and dangerous—it took very little to actually sink them.
The IJN’s goal of staying on the offensive made their aircraft carriers especially effective at weakening their opposition. The Japanese understood that attacking aircraft carriers (originally intended as a defense mechanism for fleets) could greatly weaken the US air force, making them an essential target to fight while in battle. The Japanese aircraft cannons were also notoriously strong and effective, making them an incredibly efficient offensive line. This paired well with their air fleet in general, which was known to have the offensive upper hand until 1943.
On the other hand, the American aircraft carriers were initially constructed with the sole purpose of supporting the fleet of airplanes. This made them focus on the defensive, as they were certain that the flight would continue in the skies before it found a place in the sea. However, they were eventually taken off-guard by the IJN’s strategy of bringing their aircraft carriers to the offensive line, meaning that the American forces had to adapt quickly. This doesn’t mean that the USN aircraft carriers were without some heavy equipment, though—for example, USN carriers had guns to shoot down enemy ships that may launch attacks on them. However, this was noticeably different than the Japanese carriers, which were explicitly constructed with the purpose of gunning down US aircraft carriers.
It could be argued that the amount of resources also played a role in how each nation approached the construction and execution of their aircraft carriers. For instance, in order to follow the 1922 Washington Naval Treaty (a treaty established after WWI, intending to avoid an arms race by prohibiting excess naval construction) the nations were already limited, but the USN had a significant advantage, with 135,000 tons of aircraft carriers compared to the IJN’s 81,000 tons. This access to more materials no doubt may have helped the USN to create a fleet that had more versatility, allowing them to equip their carriers with technology that would also allow them to shield themselves.
Because of the amount of resources, the American carriers were known to be sturdier and better constructed, meaning that they could hold their weight better in an intense battle. This amount of defensiveness also made them slower than the Japanese ships, meaning that they may not have been as reliable as they would have liked to be. Because the Japanese air force was incredibly strong, it was important for the USN to have aircraft carriers that provided strong support to their fleet in the event that any needed repairs or maintenance during a given mission.
Another key dividing factor in analyzing the IJN’s resources vs. the USN’s is the idea of the Pivotal Battle. This element of Japan’s doctrinal strategies showed their personal preference to other methods of wartime strategies. As a result of this, the IJN’s ships were not meant to leave a comfortable radius to their homeland or advanced bases, making them prime targets the second they were out of reach of comfort.