British troops often described the terror of jungle patrols; in addition to having to watch out for insurgent fighters, they had to navigate difficult terrain and avoid dangerous animals and insects. Many patrols would stay in the jungle for days, even weeks, without encountering the enemy and then, without warning, insurgents would ambush them. British forces, unable to distinguish from friend to foe, had to adjust to the constant risk of an insurgent attack. Such instances led to the infamous incident at Batang Kali in which 24 unarmed villagers were killed by British troops.