The advent of military aircraft made battlecruisers vulnerable to attack from above, and [[Japan]] converted some to aircraft carriers prior to [[World War II]]. With this vulnerability, they were almost obsoleted, except in the Soviet Union and later Russian Federation, the only navy with battlecruisers. | The advent of military aircraft made battlecruisers vulnerable to attack from above, and [[Japan]] converted some to aircraft carriers prior to [[World War II]]. With this vulnerability, they were almost obsoleted, except in the Soviet Union and later Russian Federation, the only navy with battlecruisers. |