防空 (ぼうくう)air defense; air defence

防空, its kanji, and other words that share them.Open this graph

Kanji in 防空

防衛ぼうえいdefense; defence
国防こくぼうnational defence; national defense
防止ぼうしprevention; check
防衛庁ぼうえいちょうJapan Defense Agency (became Ministry of Defense in January 2007)
予防よぼうprevention; precaution
攻防こうぼうoffense and defense; offence and defence
消防しょうぼうfire fighting
防災ぼうさいdisaster preparedness; prevention of damage resulting from a natural disaster
空港くうこうairport
航空こうくうaviation; flying
空からemptiness; vacuum
空気くうきair; atmosphere
航空機こうくうきaircraft
空爆くうばくaerial bombing
空間くうかんspace; room
空軍くうぐんair force

See how 防空 connects to the rest of Japanese.