Speaking of Assyria and the city of Nineveh within it, Nahum chapter 3 verses 12 & 13 say:
12 All your strongholds are fig trees with ripened figs:
If they are shaken,
They fall into the mouth of the eater.
13 Surely, your people in your midst are women!
The gates of your land are wide open for your enemies;
Fire shall devour the bars of your gates.
Nahum was saying to Assyria and the Ninevites, that their strongholds were easy pickings for their enemies. When they were attacked they would be captured with ease, like figs falling into the mouth of the eater.
As verse 13 says, one reason for that was because their gates were wide open to their enemies. Gates that should have been closed protecting them, were wide open. Why ? Because of their sin talked about in verses 1 and 4 of the chapter.
Sin makes us easy pickings for the enemy, it leaves our gates wide open.