Influence
Force
noun
Your force and power combine together to create an influence (or a force).
せいりょく
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.
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.