First Blood

First Blood is a game mechanic in Bloons TD Battles 2. To earn First Blood, the opponent's lives must be lost first without one's own lives being lost. First Blood rewards extra bonuses after battle, rewarding extra Monkey Money. If First Blood is triggered, a large text reading "First Blood" will appear on the middle of the screen. An icon of a golden skull appears on the menu of the player who won the First Blood.

Summary
To successfully get First Blood, one must cause their opponent to lose lives. The best way to do so is to go for the aggressive. Spot any weaknesses not yet noticed by the opponent and take advantage of those weaknesses with appropriate rushes.

Conversely, avoid being the first to lose lives. Don't go too ham with greeding in the early-game with Farms or Eco, because risking lives lost is just going to increase chances of voiding the First Blood privilege.

Tips

 * If you keep losing the First Blood, think about the reason behind this issue. One common example is losing the First Blood to grouped early-game rushes; use a group popper like Bomb Shooter if this keeps happening. Conversely, see if your opponent shares a similar issue.
 * One could intentionally lose First Blood as to utilize Heart of Vengeance life loss mechanic where it gains an attack speed bonus for every life lost.
 * Generally speaking, the best opportunity for First Blood is most often during the early-game, as defenses on the either player side are often at their weakest and vulnerable to early rushes. Other instances include poor camo detection.
 * If you kill the player with a rush while both player sides are at full lives, that still counts as First Blood because you'd be the first one to inflict a life-loss.

Trivia

 * "First blood" is a term that describes the first instance of shedding blood, usually in fighting competitions (e.g. boxing, fencing).
 * "First blood" is extended to apply to getting the first point or advantage in a competitive setting.
 * This is the ninth instance of blood references in the Bloons TD series. (excluding the use of "blood" or its derivatives found only in the NK blogs)
 * The first five instances of such references are found in Bloons Adventure Time TD, specifically Ricardio's Cardiovascular upgrade description, the weapon Demon Blood Sword, the trinket Demon Heart's description, Hunter Marceline's Blood Rush upgrade, and Vampire King's upgrade quote.
 * Three more blood references have followed in Bloons TD 6, the first being the Bloody Puddles map, the second being Adora's Blood Sacrifice ability, and the third being the Bloon Bleed status effect.