Final answer:
The Articles of Confederation set up a 'firm league of friendship'
Step-by-step explanation:
The document that set up a "firm league of friendship" was the Articles of Confederation. The Articles of Confederation, which were the first written constitution of the United States, established a weak central government and gave most of the power to the individual states. It aimed to create a loose alliance among the states, emphasizing cooperation and unity.
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