Answer: montenegro

AnswerCrossword Clue
MONTENEGROWhere Mikhailovitch's headquarters are.
MONTENEGROFormer kingdom, now part of Yugoslavia.
MONTENEGROKingdom, casualty of World War I.
MONTENEGRORepublic of Yugoslavia ("Black Mountain")
MONTENEGROEuropean kingdom, 1878-1918