Caesar, Legion's Emperor

Whenever you attack, you may sacrifice another creature. When you do, choose two —
• Create two 1/1 red and white Soldier creature tokens with haste that are tapped and attacking.
• You draw a card and you lose 1 life.
• Caesar deals damage equal to the number of creature tokens you control to target opponent.

Fallout

Whenever you attack, you may sacrifice another creature. When you do, choose two —
• Create two 1/1 red and white Soldier creature tokens with haste that are tapped and attacking.
• You draw a card and you lose 1 life.
• Caesar, Legion's Emperor deals damage equal to the number of creature tokens you control to target opponent.

The Soldier tokens created by Caesar's ability enter the battlefield tapped and attacking, but since they weren't declared as attacking creatures, no abilities that trigger whenever a creature attacks or whenever you attack (such as Caesar's own ability) will trigger.

You don't choose modes or a target for Caesar, Legion's Emperor's ability at the time it triggers. Rather, a second "reflexive" ability triggers when you sacrifice another creature this way. You choose modes and, if you chose the third mode, a target for that ability as it goes on the stack. Each player may respond to this triggered ability as normal.