Art of War Ch. 2: Lines of Operation — Keeping Portfolio Structure Compact

"A simple and well-defined line of operations brings swift victory; one overextended and dispersed guarantees the collapse of supply." — General Jomini

Military Context

Jomini analyses lines of operation — the routes along which an army moves supplies, reinforcements, and blows.

He demonstrates that an army working from interior lines (compact, interconnected supply routes) can concentrate and manoeuvre faster than an enemy on exterior lines (dispersed, distant, uncoordinated). Overextending the line paralyses supply and invites ambush.

Napoleon's 1812 Russian campaign is the most famous counterexample: he won nearly every engagement and lost the entire army because his supply line stretched past what could be sustained. The failure was logistical, not tactical.

The Wall Street Translation

In trading, your portfolio is your supply line. Every position requires monitoring, risk review, news tracking, and exit execution.

1. The Cost of an Overextended Portfolio

Holding 40-plus stocks across ten unrelated sectors:

• Cognitive overload: you cannot track earnings, filings, and industry developments for forty companies
• Logistical paralysis: stops get missed, sizing becomes incoherent, and gains on good names are cancelled by bad ones

2. The Advantage of Interior Lines

Keeping the book compact — say 6 to 10 names across two or three leading sectors:

• Rapid manoeuvre: you can reposition within minutes when conditions shift
• Deep research: you can genuinely master each company's earnings, management, and balance sheet

3. Prune Weak Lines Promptly

As a commander abandons secondary supply routes to reinforce the main effort, a trader must cut stagnant or losing positions and redirect the capital to leaders.

4. Compactness and Diversification Are Not in Conflict

An important clarification is needed here, or the chapter gets misread.

Jomini opposes dispersed attention, not dispersed risk. Holding a total market index fund means owning thousands of companies while occupying a single line of operation — no individual company requires tracking.

Genuine exterior-line warfare is holding 40 individual stocks that each demand research. An index fund is structurally the most extreme interior line available: maximum risk dispersion, minimum cognitive burden.

Actionable Trading Rules

1. Set a hard position limit: cap active individual holdings at ten.
2. Prune the laggards regularly: each month close the two weakest and concentrate that capital in the two strongest.
3. Cap sector exposure: no single sector above 30% of total capital.

Relevance to a Retirement Portfolio

The core insight is highly practical for retirees: separate the number of positions you must manage from the number of assets across which you bear risk.

A retirement portfolio of three or four broad index funds — domestic equities, international equities, bonds — is extremely diversified in risk and extremely compact in management. It requires one rebalance a year and no company tracking at all.

That is precisely Jomini's ideal interior line, arriving from a direction most people would not expect.