How are the fortresses like figs with Bikurim?
Rashi: All your fortified cities will be easy to capture and plunder the contents as if they are fig trees with first-fruits that ripened. When they shake the tree, they fall into the mouth of the eater. Radak - so your fortified cities will fall to the enemy. They will not help you! The fortresses are compared to figs - a person desires them, and more when they are Bikurim. So the enemy looks forward to conquering your fortresses.
Why does it say "Te'enim Im Bikurim"?
Radak: "Im Bikurim" is like v'Bikurim; also "Admoni Im Yefe Einayim" (Shmuel I, 16:12) is like v'Yefe Einayim.
Malbim: Bikurim figs fall easier than figs that are not Bikurim. So the fortresses that are Misbaker 1 now will be easier to capture.
I.e. they were made now, amidst fear of the enemy.
