aerial (adjective) – happening in the air. declassify (verb) – to declare officially that government document/report/information is no longer secret. establish (verb) – prove, demonstrate, determine, validate, verify. the fact that (phrase) – used to refer to a specific situation under consideration/discussion. grave (adjective) – crucial/critical, important/significant, serious. conflict (noun) – war, armed conflict, battle, fighting. underlying (adjective) – fundamental, basic, primary. trigger (verb) – cause, give rise to, lead to, bring about, generate, provoke, stir up. offensive (noun) – (of a weapon) suited for use in attack. invasion (noun) – attack, offensive, onslaught, incursion, assault. impose (verb) – apply, implement, enforce, force. sanctions (noun) – action taken, or an order given to force a country to obey international laws by limiting or stopping trade with that country, by not allowing economic aid for that country,