Relations between the Horn of Africa and the Arabian Peninsula go back centuries, with trade playing a key component in binding their people together. Religion has also played a part. The expansion of Wahhabism - the interpretation of Islam propagated by Saudi Arabia - has been funded by the massive oil wealth of the kingdom.
Mosques, Koranic schools and Imams have been provided with support over many years. Gradually this authoritarian form of Islam began to take hold in the Horn. While some embraced it, others didn't.
Somalia is an example. While most Somalis practised a moderate form of Suffi Islam, the Islamic fundamentalists of al-Shabaab didn't. Soon after taking control of parts of central and southern Somalia in 2009 they began imposing a much more severe form of the faith. Mosques were destroyed and the shrines of revered Suffi leaders were desecrated.
The export of faith has been followed by arms. Today the Saudis and their allies in the United Arab Emirates are exerting increasing military influence in the region.
But Saudi Arabia and other Arabian gulf states aren't the only Muslim countries that have sought influence in the region. Iran, for example, has also been an active player. In the case of Eritrea, a struggle for influence between Riyadh and Tehran has played out over the past few years. This has also been true in neighbouring Somaliland and the semi-autonomous Somali region of Puntland.
These are troubled times in the Horn of Africa. The instability that's resulted from Islamic fundamentalism, of which al-Shabaab are the best known proponents, have left the region open to outside influences. The French have traditionally had a base in Djibouti, but they have now been joined by the Americans and the Chinese.
The growing Arab military, political and religious influence is only the latest example of an external force taking hold in the region.
New powerful forces in the region
The Eritreans had been close to Iran and supported their Houthi allies in the Yemeni conflict. This was of deep concern to the Saudis, who are locked in conflict with Tehran. This is a battle for influence that pits Iranian Shias against Saudi Sunnis. Eritrea is just one of the fields on which it's being played out.
As a US cable leaked to Wikileaks put it in 2010,
The Saudi ambassador to Eritrea is concerned about Iranian influence, says Iran has supplied materiel to the Eritrean navy, and recently ran into an Iranian delegation visiting Asmara. He claims Yemeni Houthi rebels were present in Eritrea in 2009 (but is not sure if they still are), and reported that the Isaias regime this week arrested six Eritrean employees of the Saudi embassy.
Since then Eritrea has switched sides. Eritrean President, Isaias Afwerki paid a state visit to Saudi Arabia in April 2015. Not long afterwards Eritrea signed a 30-year lease on the port of Assab with the Saudis and their allies in the Emirates. The port has become a base from which to prosecute the war in Yemen. The United Nations reported that 400 Eritrean troops were now in Yemen supporting the Saudi alliance.
The United Arab Emirates has constructed a major base in Assab - complete with tanks, helicopters and barracks. In November 2016 it was reported that a squadron of nine UAE Mirage fighter planes were deployed to Eritrea from where they could attack Houthi targets on the other side of the Red Sea. In return the Gulf states agreed to modernise Asmara International Airport, increase fuel supplies to Eritrea and provide President Isaias with further funding.
Since then the United Arab Emirates has announced its intention to increase its military presence in the Horn. In January it signed an agreement to manage the Somaliland port of Berbera for 30 years. It also sought permission to have a naval base, Somaliland foreign minister Sa'ad Ali Shire told reporters.
It's true that the United Arab Emirates has submitted a formal request seeking permission to open a military base in Somaliland
The UAE are also active in the neighbouring Puntland. They have been paying for and training anti-piracy forces for years, while also financing and training its intelligence services.
They are a powerful force in the region, projecting an Arab influence as far as Madagascar and the Seychelles. It's not surprising that the United Arab Emirates was labelled "Little Sparta" by General James Mattis - now President Donald Trump's Secretary of Defence.
These are worrying times for the Ethiopian foreign ministry. Once the dominant force in the region, its influence over the Horn is now in question.
To its north the Eritreans remain implacable foes, as they have been since the border war of 1998-2000 that left these neighbours in a cold no-war, no-peace confrontation.
Addis Ababa is concerned that Eritrea's hand has become stronger in recent years. Its mining sector is looking increasingly attractive with Canadian based firms now joined by Australian and Chinese companies.
Asmara's role in the ongoing war in Yemen has allowed Eritrea to escape diplomatic isolation. The government in Asmara is now benefiting from funds and weapons, despite UN sanctions designed to prevent this from taking place.
To Ethiopia's west lies Sudan, which is also now involved in the war in Yemen, providing troops to the Saudi and United Arab Emirates backed government. These ties are said to have been cemented after the Saudis pumped a billion dollars into the Sudanese central bank. In return the Sudanese turned their backs on their former Iranian allies.
To Ethiopia's east the situation in Somalia is also of concern. No Ethiopian minister can forget the invasion of the Ogaden under President Siad Barre in 1977, when Somalia attempted to re-capture the lands lost to their neighbours during the expansionist policies of Emperor Menelik II in the nineteenth century. Siad Barre may be long gone but Ethiopian policy since the invasion has been to keep Somalia as weak and fragmented as possible.
Ethiopia has intervened repeatedly in Somalia to hold al-Shabaab at bay as well as to maintain the security of its eastern region. Addis Ababa's policy of encouraging the inherent fragmentary tendencies of the Somalis has paid dividends: the country is now a federation of states and regions. Some of these only nominally recognise the authority of the government in Mogadishu. Somaliland, in the north is close to being recognised as an independent nation. Others, like Jubaland along the Kenyan border, are under Nairobi's influence.
Martin Plaut is affiliated to the Institute of Commonwealth Studies and the Royal African Society