A fighter jet roaring through the grey sky breaks the tranquillity of a boreal forest in northern Finland, one more sign of a growing military presence that is challenging the ability of reindeer herders to exercise their livelihood. Finland, which shares a 1,340-kilometre border with Russia, dropped decades of military non-alignment to join NATO in 2023 in response to Russia's invasion of Ukraine. Reindeer herders worry that a large live-fire and combat exercise involving around 6,500 soldiers from Finland, Sweden and Britain in May would disturb the reindeer.