1845 USA annexes Texas
→ Mexican-American War
1848 USA annexes parts of Mexico
→ War between the States
1864 Prussia annexes Schleswig-Holstein
→ Wars of German unification
1898 USA annexes Hawaii
→ Spanish American War
1908 Austria-Hungary annexes Bosnia
→ First World War
1932 Japan annexes Manchuria
→ Pacific War
1938 German annexes Austria
→ Second World War
1975 North Vietnam annexes South Vietnam
→ Third Indochinese War
1991 Iraq annexes Kuwait
→ Gulf and Iraq Wars
2022 Russia annexes parts of Ukraine
→ Kaliningrad anyone…?