In force and enforce are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
In force (pronounced “in [pause] forss”) is an idiom. It can mean literally a very large group.
Enforce (pronounced “en-forss”) is a verb. It means to execute actions needed to uphold rules and laws. In the US, police are collectively called “law enforcement officers (sometimes abbreviated L-E-Os.) Enforcement is the noun version of enforce.
The following story uses both words correctly:
Eustace’s least favorite activity as a member of the HOA board was having to enforce the rules and administer fines to his non-compliant neighbors. It took several warnings before the fines started, but some people refused to change their ways.
One Saturday morning, Eustace had to buckle down and do what was necessary. A gathering of board assistants went out in force to deliver all the fine notices in person. Cue the annoyed phone calls and emails.