Due to the storm, we were obliged to cancel our picnic.

were 是 be 动词的过去式，表示过去的状态。 obliged 是动词 oblige 的过去分词形式，oblige 的意思是"迫使、使负有义务"。 to 是不定式符号，后面接动词原形，表示"去做某事"。 were obliged to 是一个固定搭配，表示"被迫做某事"或"不得不做某事"，强调由于外部原因而必须采取某种行动。