The Fire Nation divides it's land based forces into five distinct groups, which establish defensive positions in the Fire nation Captital (spot), and four denfensive positions around the main part of the archipelago (four squares). Each battalion is ready to mobilze at a moments notice, and can move to defend their areas within hours, thanks to to their new airship troop carriers.
That Navy forms a blockade around the outer islands. It is able to maintain a constant supply of reinforcements from the mainland.
Special units rallying around the Fire Sages and Sun Warriors form a chain of strongholds protecting the FNs main centers of production along the western border.
Phoenix King Axrendale appoints Azula as Supreme Commander of the Military. Her orders will be dispatched down the new chain of command, to carry out offensives in the future.
For now, the FireNation holds it's ground.
The interlocking nature of the Fire nation defensive formation ensures that an attack on any part of the FN will be met with 4500 warriors, except for the Captital and production Line, both of which can summon 6000 soldiers. The fire nation's technolgy is the best in the world, with tanks, artillery, and war balloons pouring out of the factories. All across the country, local blacksmiths and metalworkers contribute with swords and suits of armour, paid for in full by the new military fund, drawn directly from the treasury. Food reserves are booming. The Fire nation has been enjoying a time of prosperity, and is well stocked.