In warhammer 40k can space marines and imperial guard fight together?

Answer

# Imperial Guard + Space Marines (of all types except traitors) + Eldar (sometimes under certain circumstances) + [All Imperials]

# Chaos Space Marines + Chaos Daemons + any human traitors of the Imperials # Tau + Imperial Guard (under certain circumstances) # Eldar + Orks (by manipulating them) + Space Marines/Imperial Guard (under certain circumstances) # Space Marine Chapter: Soul Drinkers + Dark Eldar (happened once)