Yes, Erwin actually released a small throwing knife. Due to its size, he could easily carry the throwing knife without showing any signs of it. That was why the sneak attack succeeded.
Clovis had expected this to a certain extent, but Erwin's brilliance was beyond his imagination. He actually pushed him to the very limit so that he wouldn't think about it. That was when he launched a sneak attack.
It could be said that Erwin read him accurately.
'Poison? Nevertheless, I can't go like this. I have to defeat him before he could do something unthinkable.' Clovis decided to move toward Erwin, ignoring the knife planted on his back.
Erwin was ready to receive him as though he wanted to find another opportunity to launch a sneak attack.
But this time, Clovis decided to stop holding back.
'I'll show you the full strength that you've expected!' Clovis thought and unleashed all his swings.