An opening in a battle line that can allow an enemy to penetrate, separate units, or surround troops.

The side edge of a formation, where troops are especially vulnerable to attack from the side or rear.

What is Rightward drift?

The tendency of a Greek infantry formation to extend or slide toward its right during the advance to contact.

What is Formation cohesion?

The ability of a military formation to preserve alignment, spacing, and mutual support while moving or fighting.

What is Overlapping shields?

The practice of positioning shields so that one soldier's shield helps protect the exposed side of another.

Why Did the Phalanx Drift to the Right? — Ancient Warfare in Motion: Phalanxes, Chariots, and Siegecraft

The Battlefield Problem

A Repeated Pattern

At Mantinea in 418 BCE, both armies advanced in close order. Thucydides observed that each formation tended to extend on its right, overlapping the enemy's left.

Not a Commanded Turn

The rightward movement was not simply a general's order. It developed from many soldiers making small defensive adjustments while trying to remain part of the line.

Why the Shield Created the Drift

The Unprotected Side

The hoplite shield covered much of the left side of the body. The right side was more vulnerable, so the shield carried by the soldier to the right became important protection.

A Small Individual Adjustment

Each soldier could edge toward the man on the right and turn slightly, reducing the exposed gap. One movement was minor; repeated across hundreds of soldiers, it changed the whole line.

The Hallway Analogy

Picture the Movement

Imagine walking in a crowded hallway with your left side protected by a large bag. If the right side feels exposed, you edge toward the person on your right. The group begins to slide sideways.

From Individual to Collective

No single person needs to decide, "Turn right." Each person copies the same protective adjustment. The result is a formation that moves right even while its members intend to advance forward.

Why the Rightmost Soldier Started It

The Exposed Edge

The soldier at the extreme right lacked a comrade whose shield could protect his right side. He therefore had the greatest reason to angle away from the enemy.

A Chain Reaction

The next soldier copied the adjustment, then the next. The movement passed along the line like people making room in a row, producing a gradual rightward drift.

Cohesion Versus Protection

Two Goals at Once

A soldier had to preserve the line and protect the body. Moving closer to a neighbor helped with immediate safety, but too much movement damaged the formation's straight alignment.

Why Discipline Mattered

Formation cohesion meant more than standing shoulder to shoulder. It required soldiers to resist helpful-looking individual movements when those movements threatened the shape of the entire line.

Mantinea: When Drift Became a Gap

The Overlap

At Mantinea, the Mantinean right extended beyond the Spartan left. The normal rightward tendency had become a serious positional problem rather than a harmless sideways movement.

The Failed Correction

Agis ordered units to extend and other units to fill the resulting opening. The replacement troops did not move, leaving a gap at the moment of contact.

The Battlefield Effect

The Mantinean right and allied troops entered the unclosed gap, defeated the Spartan left, and surrounded part of it. A small movement problem became a flank and cohesion crisis.

Trace the Chain Reaction

Pause and visualize six soldiers in a row. Mark each soldier's right side as more exposed. Now move the rightmost soldier slightly away from the enemy, then let each neighbor follow while trying to keep shields overlapping. Ask: where does the line extend, and where might a gap appear? The key insight is that a defensive movement at one edge can reshape the entire battle line.

Check Understanding

Choose the explanation that best connects shield placement, individual movement, and battlefield consequences.

Why did a hoplite phalanx tend to drift to the right?

Soldiers moved toward the shield of the man on their right to protect their more exposed side, causing the whole line to slide and sometimes open gaps.
Commanders always ordered the entire formation to turn right before contact so the right wing could attack first.
The left side of every phalanx was deliberately left empty so cavalry could pass through.

Show Answer

Answer: A) Soldiers moved toward the shield of the man on their right to protect their more exposed side, causing the whole line to slide and sometimes open gaps.

The rightward drift began with the need to protect the more exposed side by overlapping with the neighbor's shield. Repeated individual adjustments shifted the formation and could create overlaps, exposed flanks, or gaps. At Mantinea, an unfilled gap helped the Mantinean right defeat the Spartan left.

Key Terms

Gap: An opening in a battle line that can allow an enemy to penetrate, separate units, or surround troops.
Flank: The side edge of a formation, where troops are especially vulnerable to attack from the side or rear.
Rightward drift: The tendency of a Greek infantry formation to extend or slide toward its right during the advance to contact.
Formation cohesion: The ability of a military formation to preserve alignment, spacing, and mutual support while moving or fighting.
Overlapping shields: The practice of positioning shields so that one soldier's shield helps protect the exposed side of another.