Assassination of Filipinos.--Many of the Filipino leaders were necessarily not well instructed in those rules for the conduct of warfare which civilized peoples have agreed upon as being humane and honorable. Many of them tried, especially in the latter months of the war, when understanding was more widely diffused, to make their conduct conform to international usage; but the revolutionary junta had committed the great crime of ordering the punishment by assassination of all Filipinos who failed to support the insurgent cause. No possible justification, in the light of modern morality, can be found for such a step as this. The very worst passions were let loose in carrying out this policy. Scores of unfortunate men were assassinated, many of them as the results of private enmity. Endless blackmail was extorted and communities were terrorized from one end of the archipelago to the other. Irregular Warfare of the Filipinos.--Through the surrender of Spanish forces, the capture of the arsenals of Cavite and Olongapo, and by purchase through Hongkong, the revolutionary government possessed between thirty thousand and forty thousand rifles. These arms were distributed to the different military zones, and the secret organization which existed in each municipality received its proportion. These guns were secreted by the different members of the command, except when occasion arose for effecting a surprise or making an attack. There were no general engagements, but in some towns there was almost nightly shooting. Pickets and small detachments were cut off, and roads became so unsafe throughout most of the archipelago that there was no travel by Americans except under heavy escort. For a long time, also, the orders of the commanding general were so lenient that it was impossible to punish properly this conduct when it was discovered. Death of General Lawton.--The American army, in its attempt to garrison every important town in the Islands, was cut up into as many as 550 small detachments of post garrisons. Thus, while there were eventually sixty thousand American soldiers in the Islands, it was rare for as many as five hundred to take the field, and most of the engagements of the year 1900 were by small detachments of fifty to one hundred men. It was in one of these small expeditions that the American army suffered the greatest single loss of the war. A few miles east of Manila is the beautiful Mariquina Valley, from which is derived the city's supply of water, and the headwaters of this pretty stream lie in the wild and picturesque fastness of San Mateo and Montalban. Although scarce a dozen miles from the capital and the headquarters of a Filipino brigade, San Mateo was not permanently occupied by the Americans until after the 18th of December, 1899, when a force under General Lawton was led around through the hills to surprise the town.