A question about first boss

[Karel]

Originally Posted by Frede

Ahh i found out why i completed the mission but never reached the 2. chapter. i didnt knew that i had to blow up the wood"tower" at the beginning of chapter 1. i always jumped over the sandbags to get in the trench (seems like a bug). so i never met the british soldat who hides himself in the trench.

thats not a bug, thats intended. Objective to destroy the wooden tower is kind of secret/optional/secondary objective, or whatever you want to call it
You do not need to complete this objective to finish the mission. As someone said here already, you can just jump down to trenches and continue in level.