https://www.pcgamer.com/civ-6-spring-update-tweaks-joint-wars-adds-12-historic-moments/

Besides Victoria's England-strengthening Pax Britannica leader bonus, Civilization 6 now lets players call for help mid-battle. 

As part of the turn-based 4X 'em up's spring update, new diplomacy tinkerings to Joint and Third Party War means players can now ask others—be that pals, strangers or AI—to join battles they're already engaged in.