The very next day her husband was called up to join the army.

was 是 be 动词的过去式，表示被动语态。 called 是动词 call 的过去分词形式，call 本意是"呼叫、召唤"。 up 在这里与 call 组成短语动词 call up，意思是"征召、召集"。 was called up 是被动语态结构，表示"被征召"。