noun
military review; military parade
Formal event where troops and equipment are inspected, often with a ceremonial parade.
国王は観兵式で部隊を閲兵した。
The king reviewed the troops at the military parade.
閲兵式 also means a military review, but 観兵式 is more commonly used in modern contexts.
Compound of 観 (view, inspect), 兵 (soldier), and 式 (ceremony). The exact historical derivation is uncertain, but the term is conventionally associated with formal military inspections.