Declare the creature that has Infantry Shield attached as an attacker. The creature triggers, creating a number of 1/1 Warrior creature tokens that are tapped and attacking equal to the creature's power.
During your postcombat main phase, activate Phyrexian Altar five times by sacrificing five Warriors, adding {3}{R}{R}.
Activate Aggravated Assault by paying {3}{R}{R}, causing you to untap all creatures you control and to get an additional combat and main phase after this one.
Repeat.

Infinite creature LTB

Infinite creature ETB

Infinite colored mana

Infinite creature sacrifice triggers

Infinite death triggers

Infinite combat phases

Infinite creature tokens

Infinite untap of creatures you control

Infinite mana creatures you control can produce

Infantry Shield

Phyrexian Altar

Aggravated Assault

Declare the creature that has Infantry Shield attached as an attacker, triggering its ability, creating a number of 1/1 Warrior creature tokens that are tapped and attacking equal to the creature's power.
Holding priority, activate Phyrexian Altar five times by sacrificing five Warriors, adding {W}{U}{B}{R}{G}.
Activate Najeela by paying {W}{U}{B}{R}{G}, untapping all attacking creatures, giving them trample, lifelink and haste, and gaining an additional combat phase after this one.
Repeat.

Infinite creature tokens with haste

Najeela, the Blade-Blossom

Declare the creature that has Infantry Shield attached as an attacker. The creature triggers, creating a number of 1/1 Warrior creature tokens that are tapped and attacking equal to the creature's power.
During your postcombat main phase, activate Thermopod five times by sacrificing five Warriors, adding {R}{R}{R}{R}{R}.
Activate Aggravated Assault by paying {3}{R}{R}, causing you to untap all creatures you control and to get an additional combat and main phase after this one.
Repeat.

Infinite red mana

Thermopod

Declare the creature that has Infantry Shield attached and Hellkite Charger as attackers, triggering the creature and Hellkite Charger. 
Resolve the creature's trigger, creating a number of 1/1 Warrior creature tokens that are tapped and attacking equal to the creature's power.
Holding priority, activate Phyrexian Altar seven times by sacrificing seven Warriors, adding {5}{R}{R}.
Resolve the Hellkite Charger trigger, causing you to pay {5}{R}{R} to untap all attacking creatures you control and to get an additional combat phase after this one.
Repeat.

Hellkite Charger

Declare the creature that has Infantry Shield attached and Hellkite Charger as attackers, triggering the creature and Hellkite Charger. 
Resolve the creature's trigger, creating a number of 1/1 Warrior creature tokens that are tapped and attacking equal to the creature's power.
Holding priority, activate Thermopod seven times by sacrificing seven Warriors, adding seven {R}.
Resolve the Hellkite Charger trigger, causing you to pay {5}{R}{R} to untap all attacking creatures you control and to get an additional combat phase after this one.
Repeat.

Combos with "Infantry Shield"