Minecraft wiki entry for Defeating_a_Nether_fortress, associated text: There is a chance that your world will not have a fortress within the four closest regions. Since the chance for a fortress to generate in a region is 2⁄5 (40%) in Java Edition and 1⁄3 (33.3%) in Bedrock Edition, There is only a 13.0% chance in Java Edition and a 19.8% chance in Bedrock Edition that this is the case. So be prepared if there are no close-by fortresses in your world, but also keep in mind that there's more likely to be a nearby fortress than if there isn't.