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Let \( G \) be a connected graph with vertex set \( V(G) \) and edge set \( E(G) \). A (defensive) alliance in \( G \) is a subset \( S \) of \( V(G) \) such that for every vertex \( v \in S \),
\[
|N[v] \cap S| \geq |N(v) \cap (V(G) – S)|.
\]
The alliance partition number, \( \psi_a(G) \), was defined (and further studied in [11]) to be the maximum number of sets in a partition of \( V(G) \) such that each set is a (defensive) alliance. Similarly, \( \psi_g(G) \) is the maximum number of sets in a partition of \( V(G) \) such that each set is a global alliance, i.e., each set is an alliance and a dominating set. In this paper, we give bounds for the global alliance partition number in terms of the minimum degree, which gives exactly two values for \( \psi_g(G) \) in trees. We concentrate on conditions that classify trees to have \( \psi_g(G) = i \) (\( i = 1, 2 \)), presenting a characterization for binary trees.