In a large pot, combine the red wine, sugar, orange slices, cloves, cinnamon sticks, nutmeg, and allspice.
Heat the mixture over medium heat until it reaches a simmer. Do not boil.
Reduce the heat to low and let the wine simmer for 20 minutes, allowing the flavors to meld together.
Remove from heat and strain out the cloves, cinnamon sticks, and orange slices.
Serve hot in mugs and garnish with additional orange slices and cinnamon sticks, if desired.