Bat Swarms are a unit of flyers, eg, they are skirmishers and have a Unit Strength of 1 per base) with the exception that their fly move is reduced to 10" instead of the usual 20".
Source: Warhammer Fantasy: 6th Edition
Bat Swarms are a unit of flyers, eg, they are skirmishers and have a Unit Strength of 1 per base) with the exception that their fly move is reduced to 10" instead of the usual 20".