Hi Chief,
Thanks for writing in.
In the Spring 2015 update for Clash, we introduced a Clan War attack confirmation screen to give players a summary of what they're attacking with. The screen also informs players that after pressing the 'Attack' button, there's no turning back, and one of your Clan War attacks will be consumed.
To study your opponent's village layout, be sure to use the 'Scout' function instead of 'Attack'. There's no way to cancel or undo an attack that has already been started, so please proceed carefully when you're at war.
If you have any other questions about Clash, please don't hesitate to contact us again.
Clash on!