during times of war The two that I know most about are his suspension of Habeas Corpus and then his issuance of the Emancipation Proclamation. On the first issue, people will often discuss that Lincoln unlawfully suspended the writ of habeas corpus during the war thus violating American Constitutional rights.
The Sahel was the last area in the northern parts of Africa, where vegetation can survive and where people were living at the time. Following the Sahel to the North one can find the Sahara desert which is a natural barrier that no invading force could trespass.
The first one is the answer ;)
