So despite not attempting a single shot on goal in the second half and outpossessed 68-32% overall, Iran had only their second win at a World Cup, the other being the 2-1 success over the US in France 20 years earlier. Then, in the second half, the banner moved up the field near the other goal.
That contrasted with the one of the main squares in Tehran, where a billboard portrays fans celebrating and holding aloft the World Cup, accompanied by the slogan "One nation, one heartbeat".
A late own goal by substitute Aziz Bouhaddouz broke Moroccan hearts in St Petersburg and sent Iran into raptures as they celebrated their second win at a World Cup with unrestrained joy. Showing just how much it meant, Iran's players threw coach Carlos Queiroz into the air after the final whistle.
This is the first World Cup for Morocco since 1998 in France and their fifth overall.
During a quick counter-attack, goalkeeper Monir El Kajoun came to Morocco's rescue as he put out his right leg to block a right-footed shot from Sardar Azmoun from close-range.
There had been excitement after officials at Tehran's Azadi Stadium announced that families would be allowed in to watch Friday's match together for the first time.
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Morocco dominated possession through the game and created a number of scoring chances, although many of them finished with shots off target.
Morocco started brilliantly, hounding Iran's every touch and swarming forward with such ferocity that on the line, Queiroz spent most of the opening 20 minutes urging his players to pause, and take a breath.
Previous meetings: The sides have never met before in official competition.
Iran made a winning start at the 2018 World Cup with a 1-0 victory over Morocco on Friday evening. The match in itself had far from the smoothness of the first half, with injuries and substitutions punctuating the entire half.
Morocco are now on a run of 18 games unbeaten, a vein of form that is only bested by Belgium (19) and Spain (20) going into Russian Federation 2018.
As for the Moroccans, they can not afford another slip-up against Portugal in Moscow on the same day. El Kaabi showed throughout the game he could dribble through the Iranian defence and caused problems for them with his strength and pace with the ball at his feet. Morocco also topped their group during the World Cup qualifiers. The team tries to win the ball aggressively and often uses long passes to the wingers who deliver crosses to the forwards.