The situation was that churches in Asia Minor, which John oversees, were dealing with false teachers who were splitting the churches. They believed Jesus was divine, but not fully human. Thus, the death & resurrection of Jesus was relatively unimportant to them — just the opposite of Christian theology: the blood of Jesus is absolutely necessary for our salvation. As John writes, he’s dealing with churches having faced the trauma of faulty theology and broken community. The answer to both is love. 
Scripture: 1 John 4:7- 21.