For more than a year and a half, brokerage companies have fought among themselves by offering popular exchange-traded funds to their customers without any commissions. Recently, the company that started the broker wars, Charles Schwab (NYSE: SCHW), took the next logical step in making its case to be the best ETF-providing broker.

The war so far
Since late 2009, nearly every major broker has gotten involved in the battle over free ETFs. After Schwab fired the first shot with its own proprietary line of ETFs, Fidelity partnered up with iShares provider BlackRock (NYSE: BLK) to give its customers access to a select set of iShares ETFs.

As time went by, the offerings got broader. Vanguard followed suit by opening up its entire line of self-managed ETFs to brokerage customers. Later, TD AMERITRADE (Nasdaq: AMTD) trumped the whole bunch with a menu of more than 100 ETFs from multiple providers. Since then, other brokers, including Scottrade, Interactive Brokers (Nasdaq: IBKR), and Firstrade have made their own plays to capture investor interest in ETFs.

The evolution of the broker wars left Schwab with only a partial victory. The company went a long way toward establishing a foothold in the ETF industry, going from zero to more than $2 billion under management by the end of last year. But in order to help its investors build a comprehensive ETF portfolio, Schwab needed to add more to its lineup of funds.

Filling in the gaps
Schwab took a big step in that direction yesterday by launching its first broad-market bond ETF. Although the Schwab U.S. Aggregate Bond ETF is actually the company's fourth ETF that focuses on fixed income, its previous offerings were oriented toward short- and intermediate-term securities as well as inflation-indexed bonds.

The new Schwab bond ETF follows the same index that heavyweight competitors Vanguard Total Bond Market (NYSE: BND) and iShares Barclays Aggregate Bond (NYSE: AGG) track. But in line with its acknowledged strategy of attempting to provide the lowest-cost ETFs available in its broadest-market categories, the Schwab bond ETF charges an expense ratio of just 0.1% annually, edging out Vanguard and representing less than half of what the iShares fund charges.

What's next?
With the new bond ETF, Schwab can now comfortably claim to give customers a way to set up a reasonably diversified asset allocation strategy. With a full slate of U.S. stock index ETFs, a trio of foreign funds that include exposure to developed and emerging-market stocks of various sizes, a fund that invests in real estate investment trusts, and now bond funds covering the full range of durations, Schwab lets you tailor your portfolio to match whatever level of risk you're comfortable with.

Of course, the bond fund doesn't exhaust the full range of ETFs that Schwab could add to its lineup in the future. Possible candidates would include a commodity-based ETF, ETFs that target specific sectors of the market, and international bond ETFs. As the continuing flood of new ETFs shows, the limit of potential ETF proliferation depends solely on the imagination of their providers and the appetite of investors.

What should you do?
I've long believed that having the right set of commission-free ETF options might well lead many investors who are seeking new brokers for their investments to select one broker over another. Despite being late to the ETF game, Schwab has done its best to catch up with its new funds, and their low expenses offset some of the possible disadvantage that comes from their being somewhat less liquid than more frequently traded ETFs from iShares, Vanguard, and State Street's (NYSE: STT) SPDR line.

That said, choosing a broker involves more than just the ETFs it offers -- especially if you plan to trade stocks, bonds, mutual funds, and other investments. But if Schwab's combination of customer service, research, and other features already entices you, having a full slate of commission-free ETFs at your disposal might well be enough to push you toward opening an account there.

Does your broker give you access to the ETFs you want? If not, you might want to consider a switch. Check out our Broker Center here to compare some of the best brokers in the business.

In the fight for the best investments, Fool contributor Dan Caplinger never surrenders. You can follow him on Twitter here. He doesn't own shares of the companies mentioned in this article. The Motley Fool owns shares of Interactive Brokers. Motley Fool newsletter services have recommended buying shares of Schwab, BlackRock, and Interactive Brokers. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Fool's disclosure policy never says die.