The whole land owned by Lord Aethelind was covered with tents and soldiers training all day and resting at night. Ten thousand men from Lucian Mithandir, two thousand from Prince Ambrose and recently fifty thousand led by general Haul joined the camp. Plus, ten thousand from Lord Aethelind as a token and show of goodwill to his friend Lucian.
Hence in total, the army loyal to Lucian Mithandir had seventy-two thousand men. It's not even half of what Lord Gandalf offered to Castellan which is one hundred and fifty thousand. Hence there were tensions in the midst of the camp, and also doubts.
Prince Ambrose's aim was to take out his brother from the crown after he just sent his sister away, and also he believed Castellan killed their father. If Castellan isn't king anymore that will mean her sister, Princess Thelma could come back home even if Taelins are no longer in power.