Sentence:  ... the step taken two or three months after the battle of Leuktra ... of causing the peace, which had already been sworn at Sparta in the preceding month of June, to be re-sworn under the presidency and guarantee of Athens, by cities binding themselves mutually to each other as defensive allies of Athens; thus silently <WSD>disenthroning</WSD> Sparta and taking her place. 
Meaning of the word marked with <WSD> tags:  To remove (someone) from their position as monarch; to deprive of a position of supremacy.