両(りょう)国(こく) ryoukokuは wa互(たが)い()に() tagaini同(どう)盟(めい) doumeiを o結(むす)ん()で()い()た() musundeita。 The two countries had formed an alliance with each other. Literal Both-countries [topic-は] mutually alliance [object-を] had-formed. 互いに (mutually) and 同盟を結ぶ (to form an alliance, literally 'to tie an alliance') are diplomatic vocabulary. 結んでいた uses ていた (past ongoing state) — the alliance existed in the past. politics
両(りょう)国(こく) ryoukokuは wa互(たが)い()に() tagaini同(どう)盟(めい) doumeiを o結(むす)ん()で()い()た() musundeita。 The two countries had formed an alliance with each other. Literal Both-countries [topic-は] mutually alliance [object-を] had-formed. 互いに (mutually) and 同盟を結ぶ (to form an alliance, literally 'to tie an alliance') are diplomatic vocabulary. 結んでいた uses ていた (past ongoing state) — the alliance existed in the past. politics