320 BC · The Nile near Memphis, Egypt
Ptolemy I held the Nile against the regent Perdiccas and Alexander's royal Macedonian army; the failed crossings cost thousands of lives and Perdiccas was murdered by his own officers, securing Ptolemaic Egypt.
Alexander died in 323 BC without a working succession. Perdiccas, holding the royal army and the regency, tried to keep the empire together; Ptolemy, governing Egypt, was busy making it his own — including by hijacking Alexander's funeral cortege and taking the body to Egypt.
That was a claim to legitimacy as much as a theft, and it made war between them certain.
Perdiccas brought the royal Macedonian army south and found Ptolemy holding the Nile. This was less a battle than a series of failed crossings: an attempt on a fort near Pelusium, then an assault on the stronghold the sources call Camels' Fort, which Ptolemy defended in person.
The worst came at a crossing near Memphis, where the river ran deeper than expected as men and animals churned the bed. Ancient accounts put the losses in the thousands, to the current and to crocodiles. Perdiccas's own officers — among them Peithon and Seleucus — killed him in his tent shortly afterwards.
Ptolemy secured Egypt without winning a pitched battle, and the dynasty he founded ruled it for three centuries, until Cleopatra. The failure also ended any real prospect of holding Alexander's empire together.
The scenario is a defence of a line that must not be crossed: Egypt wins by making every attempt expensive, Macedon by finding the crossing before its strength is spent.
The sides, the commanders and the nature of the campaign are historical. The cards and the turn economy are the game's abstraction of it.