Complex sentence: An initial wave of Cybermen arrive, but using Nardole's tricks with the explosives, they are able to make the humans appear more powerful, forcing the Cybermen to retreat and develop a new plan, giving the humans more time.
Split into simpler sentences: An initial wave of Cybermen arrive, but using Nardole's tricks with the explosives, they are able to make the humans appear more powerful. This forces the Cybermen to retreat and develop a new plan, giving the humans more time.