The period towards the end of the 15th century denotes the fall of the Swahili city states as the Portuguese period— which wasn’t a full-blown colonization effort— begun. It was a destructive time, with the sacking of places like Kilwa and Mombasa and also brought to light existing differences and power struggles between Swahili states, with the Sultan of Malindi collaborating with the Portuguese to attack Mombasa and later hoping to be named the ruler of both Mombasa and Malindi. It is the same period we see the construction of Portuguese forts along the coast with Fort Jesus in Mombasa, Vasco Da Gama pillar in Malindi and elsewhere in Pujini (Pemba), Zanzibar and Kilwa. The San Antonio de Tanna, a 17th-century Portuguese frigate that sank in Mombasa harbor in 1697 remains an intriguing underwater site.
At the same time when the Portuguese were attacking Mombasa, the Zimba tribe who were cannibals and said to have originated from southern Africa (a branch of the Zulus), were attacking Mombasa from the south and had reached Makupa right across Mombasa Island. Stories of how the Zimba had massacred 3,000 people in Kilwa had reached Mombasa. While Mombasa had repelled several Portuguese attacks (1505, 1528, 1543), it was hard to sustain the defense. This was in 1589. Mombasa had entered into an alliance with the Turkish pirates led by Mirale Beque (Amir Ali Bey) to fight off the Portuguese, who, angered by the Turkish incursion into their trade routes requested for a fleet from Goa to gain control of the island. The Portuguese had up to that point controlled the Indian ocean trade route amid opposition for Dutch, British and Turk sea merchants. Spices were in high demand then and whoever controlled the trade routes wielded a lot of power.
Entering into an alliance with the Portuguese after they had destroyed the Turks at Makupa, the Zimba were allowed to enter the Island. They massacred the people including the Sultan of Mombasa (Shehe Mvita) and occupied the island. Mirale was captured, pleaded for his life and taken to Lisbon as a prisoner where he became a Christian and lived well.
The Omani colonial period came between the late 17th to the late 19th century and his period also saw the Swahili language gain more Arabic vocabulary. Sultan bin Saif 1 from the ruling Ya’rubi clan captured Muscat and other Portuguese forts on the Coast of the Persian gulf, hence controlling the valuable trade route from Gujerat which was a big blow to the Portuguese. Again, the Ya’rubi clan led raids that ousted the Portuguese from Fort Jesus in 1698. Even so, the Prince of Faza and the Queen of Zanzibar were still allied with the Portuguese, suggesting that not everyone thought Omani rule was the solution. Later in the 18th century political power in Oman shifted to the Bus’aidi clan who changed their power base from Oman to Zanzibar, and much later in the 19th century, the Omani elite in Zanzibar were purged by the 1964 Afro-shirazi revolution
In the 19th century, European interest in Africa was looming with the 1884-5 Berlin Conference that divided Africa amongst the colonial powers. The Swahili coast however remained more of strategic place and the British were attempting to regulate and abolish slave trade. The German presence was felt as well through their exploits in German Tanganyika and Zanzibar became a port of call form where missionary work spread across other areas of the coast and inland. The British had good relations with Zanzibar and having the British Protectorate in 1890 was in a way of showing support for the sultanate.
The period also saw the spread of trade and, with it, language as Kiswahili became the lingua Franca of the region. We also see the colonial dynamics in the making of standardized Kiswahili with the British-German divided preferences on whether to use (Ki)Mvita or (Ki)Unguja in the creation of this ‘new dialect’. As individual countries in east Africa gained independence, we also see the nature of colonial influence, control and language in countries in a way that Kiswahili (or, Viswahili in respect to the diverse dialects of Kiswahili) thrive alongside French (in places like Reunion and Mayotte which are still administered by French) and Mozambique (Portuguese).