Putin's "trigger" word is NATO.
“Russia is not looking [for an enemy] but it actually sees it happening,” Peskov told reporters in Moscow. The Kremlin said it was absurd for NATO to talk of any threat from Russia and it hoped "common sense" would prevail at the Warsaw summit. "Moscow remains open to dialogue with NATO and is ready to cooperate with it", Kremlin spokesman Dmitry Peskov said in a conference call with journalists.
Russia often depicts NATO as an aggressor whose members are moving troops and military hardware further into former Soviet territory, which it regards as its sphere of influence.
BTW, Moscow has declared its intention to deploy nuclear-capable missiles in Kaliningrad, a Russian enclave between Poland and Lithuania, in response to NATO's activation of a U.S.-built missile shield on Polish soil. So when NATO deploys troops and exercises in NATO member states, that's "aggression" according to Russia, but when Russia declares its intention to deploy nuclear-capable missiles in the eastern Europe, that's just "common sense".