Without the knowledge of the context of Manga, I interpret the second line of your quote as;
We (or They) will focus the attack on this side rather than that sandbank.

“こっち側(がわ)” is a colloquial form of “こちら側,” meaning this side.“But I’ve never heard of “こっちっ側.” Actually a red warning line of the automatic spell checker pops up below “こっちっ” when I’m typing the word. It must be a typo, or very special parlance used in the Manga world.