Force
Noun
せいりょく
その武装勢力は、急速に勢力を増大している。
The armed insurgents are rapidly increasing their influence.
Your force and power combine together to create an influence (or a force).
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.