in alliance with — cooperating or working together with someone or some group

construction workers wearing different colored hard hats shake hands while holding shared blueprints. One team wears blue uniforms while the other wears orange, showing they're from separate companies. They point together at the bridge structure they're building, combining their different expertise and equipment. The blue team operates a crane while the orange team guides steel beams into position. Other workers from both teams work side by side, sharing tools and coordinating their movements. Heavy machinery from both companies operates in perfect synchronization around them. two separate groups cooperating and working together toward a common goal